Fix on Mac

[DanyPell]

At least on Mac, I had to add '-retain-symbols-file': True, #

UNSUPPORTED_LLD_FLAGS = {
# macOS-specific linker flag that libtool (ltmain.sh) will if macOS is detected.
'-bind_at_load': False,
'-retain-symbols-file': True, #
# wasm-ld doesn't support soname or other dynamic linking flags (yet). Ignore them
# in order to aid build systems that want to pass these flags.
'-soname': True,
'-allow-shlib-undefined': False,
'-rpath': True,
'-rpath-link': True,
'-version-script': True,
}