The jkernel Makefiles must be including the same gmk file twice or something. This is an indication that the makefile is malformed:

gnumake[5]: Entering directory `C:/BUILD_AREA/jdk7/jdk/make/sun/jkernel'
../../../make/common/internal/Resources.gmk:149: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/strip_prop_options'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:149: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/strip_prop_options'
../../../make/common/internal/Resources.gmk:151: warning: overriding commands for target `strip_prop_options_clean'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:151: warning: ignoring old commands for target `strip_prop_options_clean'
../../../make/common/internal/Resources.gmk:155: warning: overriding commands for target `strip_all_props'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:155: warning: ignoring old commands for target `strip_all_props'
../../../make/common/internal/Resources.gmk:238: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/compile_prop_options'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:238: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/compile_prop_options'
../../../make/common/internal/Resources.gmk:240: warning: overriding commands for target `compile_prop_options_clean'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:240: warning: ignoring old commands for target `compile_prop_options_clean'
../../../make/common/internal/Resources.gmk:244: warning: overriding commands for target `compile_all_props'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:244: warning: ignoring old commands for target `compile_all_props'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/classes'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/classes'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/CClassHeaders'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/CClassHeaders'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/obj_gO'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/obj_gO'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/bin'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/bin'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/lib'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/lib'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/lib/i386'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/lib/i386'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/lib/ext'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:49: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/lib/ext'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:149: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/strip_prop_options'
../../../make/common/internal/Resources.gmk:149: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/strip_prop_options'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:151: warning: overriding commands for target `strip_prop_options_clean'
../../../make/common/internal/Resources.gmk:151: warning: ignoring old commands for target `strip_prop_options_clean'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:155: warning: overriding commands for target `strip_all_props'
../../../make/common/internal/Resources.gmk:155: warning: ignoring old commands for target `strip_all_props'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:238: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/compile_prop_options'
../../../make/common/internal/Resources.gmk:238: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/compile_prop_options'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:240: warning: overriding commands for target `compile_prop_options_clean'
../../../make/common/internal/Resources.gmk:240: warning: ignoring old commands for target `compile_prop_options_clean'
C:/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:244: warning: overriding commands for target `compile_all_props'
../../../make/common/internal/Resources.gmk:244: warning: ignoring old commands for target `compile_all_props'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:221: warning: overriding commands for target `source_list_prime'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:221: warning: ignoring old commands for target `source_list_prime'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:224: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/.classes.list'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:224: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/.classes.list'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:227: warning: overriding commands for target `.delete.classlist'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:227: warning: ignoring old commands for target `.delete.classlist'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:233: warning: overriding commands for target `.compile.classlist'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:233: warning: ignoring old commands for target `.compile.classlist'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:259: warning: overriding commands for target `packages.clean'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:259: warning: ignoring old commands for target `packages.clean'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:273: warning: overriding commands for target `classes.clean'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:273: warning: ignoring old commands for target `classes.clean'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:302: warning: overriding commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/obj_gO/.class.headers.i586'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:302: warning: ignoring old commands for target `C:/BUILD_~1/jdk7/build/windows-i586/../windows-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/obj_gO/.class.headers.i586'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:310: warning: overriding commands for target `classheaders.clean'
C:/BUILD_AREA/jdk7/jdk/make/common/Rules.gmk:310: warning: ignoring old commands for target `classheaders.clean'
Solaris:

gnumake[5]: Entering directory `/BUILD_AREA/jdk7/jdk/make/sun/jkernel'
/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:148: warning: overriding commands for target `/BUILD_AREA/jdk7/build/solaris-i586/../solaris-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/strip_prop_options'
../../../make/common/internal/Resources.gmk:148: warning: ignoring old commands for target `/BUILD_AREA/jdk7/build/solaris-i586/../solaris-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/strip_prop_options'
/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:150: warning: overriding commands for target `strip_prop_options_clean'
../../../make/common/internal/Resources.gmk:150: warning: ignoring old commands for target `strip_prop_options_clean'
/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:154: warning: overriding commands for target `strip_all_props'
../../../make/common/internal/Resources.gmk:154: warning: ignoring old commands for target `strip_all_props'
/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:235: warning: overriding commands for target `/BUILD_AREA/jdk7/build/solaris-i586/../solaris-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/compile_prop_options'
../../../make/common/internal/Resources.gmk:235: warning: ignoring old commands for target `/BUILD_AREA/jdk7/build/solaris-i586/../solaris-i586-fastdebug/tmp/sun/sun.jkernel/jkernel/compile_prop_options'
/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:237: warning: overriding commands for target `compile_prop_options_clean'
../../../make/common/internal/Resources.gmk:237: warning: ignoring old commands for target `compile_prop_options_clean'
/BUILD_AREA/jdk7/jdk/make/common/internal/Resources.gmk:241: warning: overriding commands for target `compile_all_props'
../../../make/common/internal/Resources.gmk:241: warning: ignoring old commands for target `compile_all_props'