[macOS] flutter_desktop_darwin_unittests can be enabled for all runtime modes (#21681)

Author: iskakaushik

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -267,6 +267,7 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
   flutterArguments.command_line_argv = argv.size() > 0 ? argv.data() : nullptr;
   flutterArguments.platform_message_callback = (FlutterPlatformMessageCallback)OnPlatformMessage;
   flutterArguments.custom_dart_entrypoint = entrypoint.UTF8String;
+  flutterArguments.shutdown_dart_vm_when_done = true;
   static size_t sTaskRunnerIdentifiers = 0;
   const FlutterTaskRunnerDescription cocoa_task_runner_description = {
       .struct_size = sizeof(FlutterTaskRunnerDescription),

testing/run_tests.py

@@ -147,10 +147,6 @@ def RunCCTests(build_dir, filter):
   # These unit-tests are Objective-C and can only run on Darwin.
   if IsMac():
     RunEngineExecutable(build_dir, 'flutter_channels_unittests', filter, shuffle_flags)
-
-  # These tests can only be run on Darwin on debug mode.
-  # See: https://github.com/flutter/flutter/issues/66664
-  if IsMac() and ('debug' in build_dir):
     RunEngineExecutable(build_dir, 'flutter_desktop_darwin_unittests', filter, shuffle_flags)
 
   # https://github.com/flutter/flutter/issues/36296