Also adjust macOS comment. FreeBSD also uses clang and lld (current dev
version even uses lld as /usr/bin/ld), function-sections/gc-sections are
very well supported. It's probably a Mach-O issue on Macs.
libc++ offers std::string_view regardless of -std flag, so defining
a custom std::string_view results in a conflict.
This one is actually not a precise clone of the real one (uses two
pointers instead of pointer+length).