FIXME: Disable ubershader in NGL CI

Gets around the ubershader compile taking multiple minutes and causing
each test to timeout.

testsuite/gsk/meson.build

@@ -195,6 +195,9 @@ foreach renderer : renderers
       'G_TEST_SRCDIR=@0@'.format(meson.current_source_dir()),
       'G_TEST_BUILDDIR=@0@'.format(meson.current_build_dir())
     ]
+    if (renderer_name == 'ngl')
+      test_env += [ 'GSK_GPU_SKIP=uber' ]
+    endif
 
     if ((not testname.contains(exclude_term)) and
         (renderer_name != 'broadway' or broadway_enabled) and