Without the change gcc-12 on musl fails to build due to system headers
poisoning:
/build/build/./prev-gcc/xg++ ... ../../gcc-13-20220626/gcc/cp/mapper-resolver.cc
In file included from /<<NIX>>/musl-1.2.3-dev/include/pthread.h:30,
from /build/build/prev-x86_64-unknown-linux-musl/libstdc++-v3/include/x86_64-unknown-linux-musl/bits/gthr-default.h:35,
....
from /build/build/prev-x86_64-unknown-linux-musl/libstdc++-v3/include/memory:77,
from ../../gcc-13-20220626/gcc/../libcody/cody.hh:24,
from ../../gcc-13-20220626/gcc/cp/../../c++tools/resolver.h:25,
from ../../gcc-13-20220626/gcc/cp/../../c++tools/resolver.cc:23,
from ../../gcc-13-20220626/gcc/cp/mapper-resolver.cc:32:
/<<NIX>>/musl-1.2.3-dev/include/sched.h:84:7: error: attempt to use poisoned "calloc"
84 | void *calloc(size_t, size_t);
| ^
/<<NIX>>/musl-1.2.3-dev/include/sched.h:124:36: error: attempt to use poisoned "calloc"
124 | #define CPU_ALLOC(n) ((cpu_set_t *)calloc(1,CPU_ALLOC_SIZE(n)))
| ^
The change pulls upstream fix as is.
gcc-12 did a mass rename from .c to .cc c++ files. As a result build fails as:
substitute(): ERROR: file 'gcc/config/darwin-c.c' does not exist
Closes: https://github.com/NixOS/nixpkgs/issues/172877
