Skip test requiring os.fork

Author: msimacek

graalpython/lib-python/3/test/test_platform.py

@@ -221,7 +221,7 @@ def test_mac_ver(self):
             else:
                 self.assertEqual(res[2], 'PowerPC')
 
-
+    @support.impl_detail("fork", graalvm=False)
     @unittest.skipUnless(sys.platform == 'darwin', "OSX only test")
     def test_mac_ver_with_fork(self):
         # Issue7895: platform.mac_ver() crashes when using fork without exec