Cross compilation fails due to missing CFLAGS for the BUILD_CC

For building the build jdk, the file buildjdk-spec.gmk is used as configuration. The CLFAGS_JDKLIB in this file, does not contain -fno-lifetime-dse (and other flags) if the GCC used for BUILD_CC is newer than version 6.
Because of the missing -fno-lifetime-dse flag (and possibly others) the build jdk crashes immediately. The build JDK is not even able to run "java -version".

The reason for the missing -fno-lifetime-dse is, that during the configure step, the build system uses the target CFLAGS (provided using --with-extra-cflags) for the BUILD_CC, which is the compiler running on the host which does not support those flags.

The config.log shows the following:

configure:75323: checking if BUILD_CC supports "-fno-lifetime-dse -Werror"
configure:75341: /usr/bin/cc -c -DJAVASE_EMBEDDED -DPNG_ARM_NEON_OPT=0 -march=armv7-a -mno-unaligned-access -fsigned-char -fno-lifetime-dse -fno-delete-null-pointer-checks -fdiagnostics-color=always -fstack-protector-strong -fasynchronous-unwind-tables -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now -fno-lifetime-dse -Werror conftest.c >&5
cc: error: unrecognized command line option '-mno-unaligned-access'; did you mean '-Wno-aligned-new'?
configure:75341: $? = 1

Most of the flags provided to /usr/bin/cc are identical with those provided to configure via --with-extra-cflags.

This does not only happen while configure checks for the flag -fno-lifetime-dse, but also for "-fno-delete-null-pointer-checks", "-ffp-contract=off" and possibly others.

This only happens for the CFLAGS, but not for CXXFLAGS. Checking the c++ compiler works as expected:

configure:75440: checking if BUILD_CXX supports "-fno-lifetime-dse -Werror"
configure:75458: /usr/bin/g++ -c -fno-lifetime-dse -Werror conftest.cpp >&5
configure:75458: $? = 0
configure:75473: result: yes

GCCs used during compilation:

gcc (Debian 8.3.0-6) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

arm-linux-gnueabi-gcc (Linaro GCC 4.9-2017.01) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.