bpo-46633: Skip tests on ASAN and/or MSAN builds (GH-31632)

Skip tests on ASAN and/or MSAN builds:

* multiprocessing tests
* test___all__
* test_concurrent_futures
* test_decimal
* test_peg_generator
* test_tools

The ASAN job of GitHub Actions no longer excludes these tests.

Lib/test/test_decimal.py

@@ -34,7 +34,7 @@ import numbers
 import locale
 from test.support import (run_unittest, run_doctest, is_resource_enabled,
                           requires_IEEE_754, requires_docstrings,
-                          requires_legacy_unicode_capi)
+                          requires_legacy_unicode_capi, check_sanitizer)
 from test.support import (TestFailed,
                           run_with_locale, cpython_only,
                           darwin_malloc_err_warning)
@@ -43,17 +43,6 @@ from test.support import warnings_helper
 import random
 import inspect
 import threading
-import sysconfig
-_cflags = sysconfig.get_config_var('CFLAGS') or ''
-_config_args = sysconfig.get_config_var('CONFIG_ARGS') or ''
-MEMORY_SANITIZER = (
-    '-fsanitize=memory' in _cflags or
-    '--with-memory-sanitizer' in _config_args
-)
-
-ADDRESS_SANITIZER = (
-    '-fsanitize=address' in _cflags
-)
 
 
 if sys.platform == 'darwin':
@@ -5518,7 +5507,8 @@ class CWhitebox(unittest.TestCase):
     # Issue 41540:
     @unittest.skipIf(sys.platform.startswith("aix"),
                      "AIX: default ulimit: test is flaky because of extreme over-allocation")
-    @unittest.skipIf(MEMORY_SANITIZER or ADDRESS_SANITIZER, "sanitizer defaults to crashing "
+    @unittest.skipIf(check_sanitizer(address=True, memory=True),
+                     "ASAN/MSAN sanitizer defaults to crashing "
                      "instead of returning NULL for malloc failure.")
     def test_maxcontext_exact_arith(self):