Issue #22332: test_multiprocessing_main_handling is now skipped if sem_open

implementation is broken (ex: skipped on FreeBSD 6.4).

Lib/test/test_multiprocessing_main_handling.py

@@ -22,6 +22,9 @@ from test.script_helper import (
 import multiprocessing
 AVAILABLE_START_METHODS = set(multiprocessing.get_all_start_methods())
 
+# Issue #22332: Skip tests if sem_open implementation is broken.
+support.import_module('multiprocessing.synchronize')
+
 verbose = support.verbose
 
 test_source = """\