Use remove_build_metadata.py on all the trybots (take 2).

scripts/slave/recipes/chromium_trybot.expected/swarming_missing_isolated.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_chromium_rel",
@@ skipping 216 matching lines @@
       "browser_tests",
       "browser_tests_run",
       "chrome"
     ],
     "name": "compile (with patch)"
   },
   {
     "cmd": [
       "python",
       "-u",
+      "[BUILD]/scripts/slave/recipe_modules/isolate/resources/remove_build_metadata.py",
+      "--build-dir",
+      "[SLAVE_BUILD]/src/out/Release",
+      "--src-dir",
+      "[SLAVE_BUILD]/src"
+    ],
+    "cwd": "[SLAVE_BUILD]",
+    "name": "remove_build_metadata"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "[BUILD]/scripts/slave/recipe_modules/isolate/resources/find_isolated_tests.py",
       "--build-dir",
       "[SLAVE_BUILD]/src/out/Release",
       "--output-json",
       "/path/to/tmp/json"
     ],
     "name": "find isolated tests",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"base_unittests\": \"[dummy hash for base_unittests]\"@@@",
@@ skipping 273 matching lines @@
       "@@@STEP_TEXT@TEST RESULTS WERE INVALID@@@",
       "@@@STEP_FAILURE@@@"
     ]
   },
   {
     "name": "$final_result",
     "reason": "Step('browser_tests') failed with return_code 1",
     "status_code": 1
   }
 ]