Centralized test command argument in .pyl configuration.

* Remove args from gn_isolate_map.pyl
* Set idempotent to false for performance tests

Bug: webrtc:13899
Change-Id: Icde80af02070e024c1292721db9c0b8a4d906343
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258685
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Jeremy Leconte <jleconte@google.com>
Cr-Commit-Position: refs/heads/main@{#36531}

tools_webrtc/mb/mb.py

@@ -88,7 +88,7 @@ class WebRTCMetaBuildWrapper(mb.MetaBuildWrapper):
     elif is_ios:
       cmdline += [
           vpython_exe, '../../tools_webrtc/flags_compatibility.py',
-          'bin/run_%s' % target, '--out-dir', '${ISOLATED_OUTDIR}'
+          'bin/run_%s' % target
       ]
       extra_files.append('../../tools_webrtc/flags_compatibility.py')
     elif test_type == 'raw':