[gentoo-user] Can't rebuild gentoo kernel-4.9.16 with gcc-5.4.0

[Mick]

I tried to change the kernel config file and then rebuild the kernel, but it 
fails like this on two up to date stable systems:

# make && make modules_install && make firmware_install
  HOSTCC  scripts/kconfig/conf.o
  HOSTLD  scripts/kconfig/conf
scripts/kconfig/conf  --silentoldconfig Kconfig
  HOSTCC  arch/x86/tools/relocs_32.o
  HOSTCC  arch/x86/tools/relocs_64.o
  HOSTCC  arch/x86/tools/relocs_common.o
  HOSTLD  arch/x86/tools/relocs
  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CC      arch/x86/purgatory/purgatory.o
  AS      arch/x86/purgatory/stack.o
  AS      arch/x86/purgatory/setup-x86_64.o
  CC      arch/x86/purgatory/sha256.o
  AS      arch/x86/purgatory/entry64.o
  CC      arch/x86/purgatory/string.o
  LD      arch/x86/purgatory/purgatory.ro
  BIN2C   arch/x86/purgatory/kexec-purgatory.c
  CC      kernel/bounds.s
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CC      arch/x86/kernel/asm-offsets.s
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  DESCEND  objtool
make[4]: *** No rule to make target '/usr/lib/gcc/x86_64-pc-linux-
gnu/4.9.4/include/stddef.h', needed by '/usr/src/linux-4.9.16-
gentoo/tools/objtool/fixdep.o'.  Stop.
make[3]: *** [Makefile:42: /usr/src/linux-4.9.16-gentoo/tools/objtool/fixdep-
in.o] Error 2
make[2]: *** [/usr/src/linux-4.9.16-gentoo/tools/build/Makefile.include:4: 
fixdep] Error 2
make[1]: *** [Makefile:60: objtool] Error 2
make: *** [Makefile:1614: tools/objtool] Error 2


# gcc-config -l
 [1] x86_64-pc-linux-gnu-5.4.0 *


Why is this happening and how can I fix it?  Running fix_libtool.sh on 4.9.4 
doesn't change anything.  :-/

Am I supposed to emerge a later version gentoo-sources to be able to build a 
kernel with gcc-5.4.0?
-- 
Regards,
Mick