profiles: core: fix NIX_CFLAGS_COMPILE_x86_64_unknown_linux_gnu variable
Fixes Clang and GCC not suppressing warnings in system headers because they weren't marked as such.
For example, given the following a.c file:
#include <limits.h>
int main(void) {}
Before this patch:
[epita@nixos:~]$ clang -std=c99 -pedantic -Werror -Wall -Wextra -Wvla a.c
In file included from a.c:1:
/run/current-system/sw/include/limits.h:124:3: error: #include_next is a language extension [-Werror,-Wgnu-include-next]
# include_next <limits.h>
^
1 error generated.
[epita@nixos:~]$ gcc -std=c99 -pedantic -Werror -Wall -Wextra -Wvla a.c
In file included from a.c:1:
/run/current-system/sw/include/limits.h:124:3: error: #include_next is a GCC extension [-Werror]
124 | # include_next <limits.h>
| ^~~~~~~~~~~~
cc1: all warnings being treated as errors
[epita@nixos:~]$
After this patch:
[epita@nixos:~]$ clang -std=c99 -pedantic -Werror -Wall -Wextra -Wvla a.c
[epita@nixos:~]$ gcc -std=c99 -pedantic -Werror -Wall -Wextra -Wvla a.c
[epita@nixos:~]$