Merge pull request #139748 from trofi/fix-py3c

py3c: unconditionally drop -Werror (fix gcc-11 build)

pkgs/development/libraries/py3c/default.nix

···
     sha256 = "04i2z7hrig78clc59q3i1z2hh24g7z1bfvxznlzxv00d4s57nhpi";
   };
 
-  postPatch = lib.optionalString stdenv.cc.isClang ''
+  postPatch = ''
+    # clang and gcc-11 complain about 'register' keywords used by
+    # python-2.7. Let's avoid blanket -Werror.
     substituteInPlace test/setup.py \
       --replace "'-Werror', " ""
   '';