rpcgen: Skip generator tests on macOS

The generator can produce different code on Linux and macOS:
specifically, on the former we want to use xdr_uint64_t while
the latter needs xdr_u_int64_t instead.

This is clearly a problem for tests that involve comparing the
output produced against some expected output that's stored in
the git repository.

In the long run, we need to find a better way to handle this,
but since 9.10.0 is going to be released very soon and we don't
want it to have a broken test suite on macOS, simply skip the
generator tests on that platform for now.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

scripts/rpcgen/meson.build

@@ -3,7 +3,7 @@ subdir('rpcgen')
 if tests_enabled[0]
   subdir('tests')
 
-  if pytest_prog.found()
+  if pytest_prog.found() and host_machine.system() != 'darwin'
     test(
       'rpcgen-pytest',
       python3_prog,