Fix Meson build failures by separating macOS compile-time and link-time flags

[JanisErdmanis]

This is from PR that rebuilds Libepoxy JuliaPackaging/Yggdrasil#11040

# meson unconditionally (?) adds the command line argument
# `-Werror=unused-command-line-argument`. That would be fine, except
# that we (the `cc` script) add `-Wl,-sdk_version,11.0` on Darwin,
# which is actually unused when meson checks for supported compiler
# options. This means that each such check fails, and meson won't use
# any options. That's mostly fine, except for the option
# `-Wno-int-conversion` which is required by the source code.
#
# The code below modifies the `cc` script to filter out the option
# `-Werror=unused-command-line-argument`. This should arguably either
# happen by default, or `cc` should only add the
# `-Wl,-sdk_version,11.0` when the linker is actually called.
#
# We modify `cc` on all architectures to prevent possible similar
# errors there.

This fix was what I got from Claude. I haven't tested it locally. It may break things in unintended ways.