build: suppress "ignoring duplicate libraries" warning on macOS
Xcode 15, which provides the compiler toolchain for building libvirt
on macOS has switched to a new linker that warns about duplicated
"-lblah" options on the ld commandline. In practice this is impossible
to prevent in a large project, and also harmless.
Fortunately the new ld command also has an option,
-no_warn_duplicate_libraries, that supresses this harmless/pointless
warning, meson has a simple way to check if that option is supported,
and libvirt's meson.build files already have examples of adding an
option to the ld commandline if it's available.