Add a ios_x64_dbg_simulator try bot.

The goal of this bot is to replace ios_sim_x64_dbg_ios(12, 13 and 14).

Change-Id: I6d8f5004a9440f5fd8cb96730dc2dbb4abba2e61
Bug: b/264630045
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/290893
Commit-Queue: Jeremy Leconte <jleconte@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39086}
diff --git a/infra/specs/generate_buildbot_json.py b/infra/specs/generate_buildbot_json.py
index aa03751..43ae366 100755
--- a/infra/specs/generate_buildbot_json.py
+++ b/infra/specs/generate_buildbot_json.py
@@ -55,7 +55,12 @@
       seen_mixins = seen_mixins.union(tester.get('mixins', set()))
   for suite in generator.test_suites.values():
     for test in suite.values():
-      seen_mixins = seen_mixins.union(test.get('mixins', set()))
+      if isinstance(test, list):
+        # This is for mixins defined in variants.pyl.
+        for variant in test:
+          seen_mixins = seen_mixins.union(variant.get('mixins', set()))
+      else:
+        seen_mixins = seen_mixins.union(test.get('mixins', set()))
 
   found_mixins = ast.literal_eval(open(WEBRTC_MIXIN_FILE_NAME).read())
   for mixin in seen_mixins: