The stage1 gcc build runs with --without-headers, but all-target-libgcc was
still pulling in gthr-default.h and failing on missing pthread.h.
Adjust steps-guix/gcc-15.2.0/pass1.sh configure flags to match a headers-free
bootstrap profile:
- add --disable-threads
- add --disable-shared
- add --disable-libssp
- add --disable-libsanitizer
- add --disable-libquadmath
- add --disable-libatomic
- add --disable-libgomp
Keep the existing multilib bootstrap flow:
- make all-gcc
- make all-target-libgcc
- make install-gcc
- make install-target-libgcc
- add gcc-15.2.0 to steps-guix manifest after binutils-2.41
- keep full gcc-15.2.0 pass1 src_prepare cleanup/regeneration flow
- switch configure/build/install to kernel toolchain bootstrap mode:
--without-headers, --enable-multilib, all-gcc, all-target-libgcc
- install into /kernel-toolchain and prioritize /kernel-toolchain/bin in PATH
- add missing gcc distfiles entry for SARIF spec
- include decDPD helper files used during src_prepare