Try returning to runInShell:true to see if that fixes the CI hang

Author: stuartmorgan-g

packages/pigeon/tool/run_tests.dart

@@ -239,7 +239,9 @@ Future<int> _runMockHandlerTests() async {
 
 Future<int> _runWindowsUnitTests() async {
   const String examplePath = './$testPluginRelativePath/example';
-  final int compileCode = await runFlutterBuild(examplePath, 'windows');
+  final int compileCode = await runProcess(
+      'flutter', <String>['build', 'windows', '--debug'],
+      workingDirectory: examplePath, runInShell: true);
   if (compileCode != 0) {
     return compileCode;
   }

packages/pigeon/tool/shared/process_utils.dart

@@ -14,11 +14,13 @@ Future<Process> _streamOutput(Future<Process> processFuture) async {
 Future<int> runProcess(String command, List<String> arguments,
     {String? workingDirectory,
     bool streamOutput = true,
-    bool logFailure = false}) async {
+    bool logFailure = false,
+    bool runInShell = false}) async {
   final Future<Process> future = Process.start(
     command,
     arguments,
     workingDirectory: workingDirectory,
+    runInShell: runInShell,
   );
   final Process process = await (streamOutput ? _streamOutput(future) : future);
   final int exitCode = await process.exitCode;