On gcc-11 build fails as:
$ nix-build -E 'with import ./. {}; py3c.override { stdenv = gcc11Stdenv; }'
gcc -fno-strict-aliasing ... -Werror -Wall
cc1plus: warning:
command-line option '-Wstrict-prototypes' is valid for C/ObjC but not for C++
In file included from /nix/store/...-python-2.7.18/include/python2.7/Python.h:88,
from test_py3c.cpp:4:
/nix/store/...-python-2.7.18/include/python2.7/unicodeobject.h:534:24:
error: ISO C++17 does not allow 'register' storage class specifier [-Werror=register]
534 | register PyObject *obj, /* Object */
| ^~~
The fix was already present o clang toolchain. Let's extendt it to all toolchains.
