[tools] run-tests.py

List all variants for the --variant help text

Change-Id: I249d8140b19e13dc3eceedaade2b856b1fdb1567
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3663088Reviewed-by: Liviu Rau <liviurau@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80884}

tools/testrunner/standard_runner.py

@@ -90,9 +90,10 @@ class StandardTestRunner(base_runner.BaseTestRunner):
                       help='Deprecated. '
                            'Equivalent to passing --variants=default',
                       default=False, dest='no_variants', action='store_true')
-    parser.add_option('--variants',
-                      help='Comma-separated list of testing variants;'
-                      ' default: "%s"' % ','.join(VARIANTS))
+    parser.add_option(
+        '--variants',
+        help='Comma-separated list of testing variants;'
+        ' default: "%s"' % ','.join(ALL_VARIANTS))
     parser.add_option('--exhaustive-variants',
                       default=False, action='store_true',
                       help='Deprecated. '