Makefile: ignore unused argument warning when linking

[BouncyMaster]

Summary

None

Purpose of change

At least on OpenBSD with clang, passing -stdlib=libc++ when linking gives this error:

clang++: error: argument unused during compilation: '-stdlib=libc++'   [-Werror,-Wunused-command-line-argument]

Although not passing the argument when linking works on OpenBSD, it does not on Linux with clang and USE_LIBCXX=1.

Describe the solution

We ignore the warning we might get on BSDs while keeping the argument for systems where it is actually needed.

Describe alternatives you've considered

Not passing -stdlib=libc++ to LDFLAGS if building on BSDs. However, testing if the behaviour is the same on all other BSDs would be time consuming.

Testing

Successfully built tiles on OpenBSD with clang with this change.

Additional context

This is a continuation of this closed PR: #60208

[andrei8l]

You could try to figure out if libc++ is used by default with something like echo 'int main(){}' | clang++ -x c++ - && ldd a.out|grep libc\+\+ and only passing the parameter if it's not.

[BrettDong]

There is a catch, the ldd command does not exist on macOS.

[stale[bot]]

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