Remove `-lstdc++fs` from the default link flags

Fix for Clang not working with MacOS

On MacOS and (I think) most BSDs the default standard library is libc++, and so attempting to link with libstdc++fs does not work.

On Linux, where (AFAIK) most distros use Clang/libstdc++, this is going to mean link-time failures when using std::filesystem. In this case the user can add Link-Flags: -lstdc++fs to their toolchain file themselves as a fix.

This is intended to fix #11.

Unfortunately I haven't been able to successfully build DDS yet to actually try it out, but looking at the surrounding code it seems like the right solution...

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