meson: Don't attempt to use version scripts on macOS

macOS libraries don't support symbol versioning, so the only
result that we achieve by passing additional flags to the linker
is a bunch of messages like

  ld: warning: ignoring file .../libvirt/build/src/libvirt.syms,
  building for macOS-x86_64 but attempting to link with file built
  for unknown-unsupported file format ( 0x23 0x20 0x57 0x41 ... )

being produced during the build.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

meson.build

@@ -510,6 +510,9 @@ libvirt_no_indirect = cc.get_supported_link_arguments([
 
 if host_machine.system() == 'windows'
   version_script_flags = '-Wl,'
+elif host_machine.system() == 'darwin'
+  # macOS libraries don't support symbol versioning
+  version_script_flags = ''
 else
   test_file = '@0@/src/libvirt_qemu.syms'.format(meson.source_root())
   if cc.has_link_argument('-Wl,--version-script=@0@'.format(test_file))