cc: Remove explicit CXX_FLAG

[dmadisetti]

Ran workflows on my branch and it seemed to work (except the hooks that need buildbuddy) https://github.com/AnotherGroupChat/rules_nixpkgs/actions/runs/2157830144

Just seeing how #218 influences your tests. Let me know if there is a better way- but vanilla bazel does not add this flag

Opening as a draft as you all may have better ideas on how to implement this

[aherrmann]

See https://github.com/tweag/rules_nixpkgs/issues/218#issuecomment-1097644432 for why -x c++ was added.

[evertedsphere]

@dmadisetti is this still something you need? It seems like the upstream fix at https://github.com/bazelbuild/bazel/issues/15499 is also stalled.

[evertedsphere]

See #298.

[evertedsphere]

Done in #298.