cc-wrapper: Enter C++ mode when -lc++ is passed

[judofyr]

Description of changes

When linking C++ programs in LLVM we're currently explicitly passing in -lc++abi as this appears to be required by recent versions of Clang. However, it also appears to b common for packages to use the C compiler to link binaries which uses C++, in which case they do pass in -lc++. This changes the wrapper to also take this into consideration and enter "C++ mode" whenever -lc++ is passed as an argument.

Fixes #166205.
Fixes #150655

Things done

I'm very new to nixpkgs and haven't really tested this change directly. I did manually apply the same patch in a local version of the cc-wrapper script and saw that I was able to link C++ binaries using the C compiler (more specifically: I was able to build Postgis).

I believe this change will cause quite a lot of rebuilds? Hence I targeted the staging branch.

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

Priorities

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[ghost]

Is this ever necessary with gcc?

If not, could we make this behavior isClang-specific?

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/nix-macos-monthly/12330/49

[hzeller]

To clarify, this change is only intending to fix linking, right @Artturin ?

The matter of the #150655 bug was about finding the c++ headers when clang is invoked with a c++ file (it only works if explicitly invoked with clang++ which is unlike any other Linux distribution).

I verified that the following would not be resolved with this PR:

nix-shell  \
    -E '{ pkgs ? import <nixpkgs> {} }: pkgs.clang13Stdenv.mkDerivation { name="foo";}' \
    --run 'echo "#include <vector>" > /tmp/foo.cc ; clang -c /tmp/foo.cc -o /tmp/foo.o'

[ghost]

superseded by #292043 which fixes the build.