Use src-side launcher for telemetry_unittests in chromium_trybot recipe

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_arm",
@@ skipping 88 matching lines @@
       "@@@STEP_LOG_LINE@json.output@    }@@@",
       "@@@STEP_LOG_LINE@json.output@  ]@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
+      "[SLAVE_BUILD]/src/testing/scripts/get_compile_targets.py",
+      "--output",
+      "/path/to/tmp/json",
+      "--",
+      "--build-config-fs",
+      "Release",
+      "--paths",
+      "{\"build\": \"[BUILD]\"}",
+      "--properties",
+      "{\"buildername\": \"linux_arm\", \"buildnumber\": 571, \"slavename\": \"TestSlavename\"}"
+    ],
+    "name": "get compile targets for scripts",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@json.output@{}@@@",
+      "@@@STEP_LOG_END@json.output@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "env": {
       "GYP_CROSSCOMPILE": "1",
       "GYP_DEFINES": "arm_float_abi=hard component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=arm test_isolation_mode=archive test_isolation_outdir=https://isolateserver.appspot.com use_goma=1"
     },
     "name": "gclient runhooks (with patch)"
   },
   {
@@ skipping 43 matching lines @@
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"dummy_target_1\": \"[dummy hash for dummy_target_1]\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"dummy_target_2\": \"[dummy hash for dummy_target_2]\"@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@",
       "@@@SET_BUILD_PROPERTY@swarm_hashes@{\"dummy_target_1\": \"[dummy hash for dummy_target_1]\", \"dummy_target_2\": \"[dummy hash for dummy_target_2]\"}@@@"
     ]
   }
 ]