During a control build on Windows:

make[2]: Leaving directory `/cygdrive/g/tbell/6523947/jaxws/make'
/usr/bin/mkdir -p g:/tbell/6523947/build/windows-i586/hotspot/outputdir
/usr/bin/mkdir -p g:/tbell/6523947/build/windows-i586/hotspot/import
cd ./hotspot/make && \
    make JDK_TOPDIR=g:/tbell/6523947/jdk JDK_MAKE_SHARED_DIR=g:/tbell/6523947/jdk/make/common/shared EXTERNALSANITYCONTROL=true TARGET_CLASS_VERSION=5 MILESTONE=internal BUILD_NUMBER=b191 JDK_BUILD_NUMBER=b191 FULL_VERSION=1.7.0-internal-b191 PREVIOUS_JDK_VERSION=1.6.0 JDK_VERSION=1.7.0 JDK_MKTG_VERSION=7 JDK_MAJOR_VERSION=1 JDK_MINOR_VERSION=7 JDK_MICRO_VERSION=0 PREVIOUS_MAJOR_VERSION=1 PREVIOUS_MINOR_VERSION=6 PREVIOUS_MICRO_VERSION=0 ARCH_DATA_MODEL=32 COOKED_BUILD_NUMBER=191 ANT_HOME="/cygdrive/g/ant/1.7.0" FINDBUGS_HOME="/cygdrive/g/findbugs/findbugs-1.2.1" ALT_OUTPUTDIR=g:/tbell/6523947/build/windows-i586/hotspot/outputdir ALT_EXPORT_PATH=g:/tbell/6523947/build/windows-i586/hotspot/import ALT_SLASH_JAVA=J: ALT_BOOTDIR=C:/jdk1.6.0_03 ALT_LANGTOOLS_DIST=g:/tbell/6523947/build/windows-i586/langtools/dist all_product
make[2]: Entering directory `/cygdrive/g/tbell/6523947/hotspot/make'
cd /cygdrive/g/tbell/6523947/hotspot/make; \
make VM_TARGET=product generic_build2 ALT_OUTPUTDIR=g:/tbell/6523947/build/windows-i586/hotspot/outputdir
make[3]: Entering directory `/cygdrive/g/tbell/6523947/hotspot/make'
mkdir -p g:/tbell/6523947/build/windows-i586/hotspot/outputdir
cd g:/tbell/6523947/build/windows-i586/hotspot/outputdir; \
    MAKEFLAGS= MFLAGS= nmake /NOLOGO -f g:/tbell/6523947/hotspot/build/windows/build.make \
Variant=compiler2 \
                      WorkSpace=g:\\tbell\\6523947\\hotspot \
BootStrapDir=C:\\jdk1.6.0_03 \
                      BuildUser=Administrator \
ARCH=x86 BUILDARCH=i486 Platform_arch=x86 Platform_arch_model=x86_32 JDK_MKTG_VERSION=7 JDK_MAJOR_VER=1 JDK_MINOR_VER=7 JDK_MICRO_VER=0 JDK_BUILD_NUMBER=191 JAVA_HOME=C:\\jdk1.6.0_03 GAMMADIR=g:\\tbell\\6523947\\hotspot MAKE_VERBOSE=y HOTSPOT_RELEASE_VERSION=13.0-b02 JRE_RELEASE_VERSION=1.7.0-internal-b191 HOTSPOT_BUILD_VERSION= product
NMAKE : fatal error U1052: file 'g:/tbell/6523947/hotspot/build/windows/build.make' not found

Stop.

make[3]: *** [generic_build2] Error 2
make[3]: Leaving directory `/cygdrive/g/tbell/6523947/hotspot/make'
make[2]: *** [product] Error 2
make[2]: Leaving directory `/cygdrive/g/tbell/6523947/hotspot/make'
make[1]: *** [hotspot-build] Error 2
make[1]: Leaving directory `/cygdrive/g/tbell/6523947'
make: *** [product_build] Error 2
(control build log file attached as product_build.log)