Modify 'build_dir' for run_mb() to avoid double 'Debug'

scripts/slave/recipes/blimp/integration.expected/Blimp_Client_Engine_Integration_test_pass.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': '.DEPS.git', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}]\ntarget_os = ['android']",
       "--patch_root",
       "src",
@@ skipping 237 matching lines @@
       "TestSlavename",
       "--goma-deps-cache-file",
       "Blimp_Client_Engine_Integration.gomadeps",
       "--compiler",
       "goma",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
       "--goma-service-account-json-file",
       "/creds/service_accounts/service-account-goma-client.json",
       "--out-dir",
-      "[SLAVE_BUILD]/src/out-linux/Debug",
+      "[SLAVE_BUILD]/src/out-linux",
       "--goma-dir",
       "[CACHE]/cipd/goma",
       "--",
       "blimp"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "compile",
@@ skipping 52 matching lines @@
       "TestSlavename",
       "--goma-deps-cache-file",
       "Blimp_Client_Engine_Integration.gomadeps",
       "--compiler",
       "goma",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
       "--goma-service-account-json-file",
       "/creds/service_accounts/service-account-goma-client.json",
       "--out-dir",
-      "[SLAVE_BUILD]/src/out-android/Debug",
+      "[SLAVE_BUILD]/src/out-android",
       "--goma-dir",
       "[CACHE]/cipd/goma",
       "--",
       "blimp",
       "chrome_public_apk"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "compile (2)",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]