Support (LLVM) libc++ on other platforms such as linux

[theoparis]

See https://github.com/mlua-rs/luau-src-rs/blob/main/src/lib.rs#L243
LLVM libc++ is currently only supported on apple platforms.

I get a bunch of linking errors due to this:

  ld.lld: error: undefined symbol: std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::append(char const*)
          >>> referenced by string:1361 (/home/theo/src/llvm-builds/install/bin/../include/c++/v1/string:1361)
          >>>               93bf4816e2ff97ae-Compiler.o:(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::operator+=[abi:ne200000](char const*)) in archive /home/theo/src/car-thing-tools/target/debug/deps/libmlua_sys-905d254762e6b864.rlib

[khvzak]

Could you try the latest release (0.640), or if it does not work, steps how to reproduce the issue?

[theoparis]

Hmm it did work but I had to add -Clink-arg=-lc++abi to RUSTFLAGS for some reason.