Pass --local-engine* flags from dev/bots/test.dart down to `pub test` via env variables (#71721)

dev/bots/test.dart

@@ -56,6 +56,8 @@ final String flutterTester = path.join(flutterRoot, 'bin', 'cache', 'artifacts',
 /// configuration) -- prefilled with the arguments passed to test.dart.
 final List<String> flutterTestArgs = <String>[];
 
+final Map<String, String> localEngineEnv = <String, String>{};
+
 final bool useFlutterTestFormatter = Platform.environment['FLUTTER_TEST_FORMATTER'] == 'true';
 
 
@@ -105,6 +107,13 @@ Future<void> main(List<String> args) async {
   print('$clock STARTING ANALYSIS');
   try {
     flutterTestArgs.addAll(args);
+    for (final String arg in args) {
+      if (arg.startsWith('--local-engine='))
+        localEngineEnv['FLUTTER_LOCAL_ENGINE'] = arg.substring('--local-engine='.length);
+      if (arg.startsWith('--local-engine-src-path='))
+        localEngineEnv['FLUTTER_LOCAL_ENGINE_SRC_PATH'] = arg.substring('--local-engine-src-path='.length);
+    }
+
     if (Platform.environment.containsKey(CIRRUS_TASK_NAME))
       print('Running task: ${Platform.environment[CIRRUS_TASK_NAME]}');
     print('═' * 80);
@@ -1242,6 +1251,7 @@ Future<void> _pubRunTest(String workingDirectory, {
   ];
   final Map<String, String> pubEnvironment = <String, String>{
     'FLUTTER_ROOT': flutterRoot,
+    ...localEngineEnv
   };
   if (Directory(pubCache).existsSync()) {
     pubEnvironment['PUB_CACHE'] = pubCache;