[flutter_tools] fix flutter create -t skeleton (#141233)

Fixes https://github.com/flutter/flutter/issues/139138

This had been broken since https://github.com/flutter/flutter/pull/130090 merged, however, the test happened run with flutter_tools/pubspec.yaml in the current working directory.

packages/flutter_tools/lib/src/localizations/gen_l10n.dart

@@ -48,7 +48,7 @@ Future<LocalizationsGenerator> generateLocalizations({
   precacheLanguageAndRegionTags();
 
   // Use \r\n if project's pubspec file contains \r\n.
-  final bool useCRLF = fileSystem.file('pubspec.yaml').readAsStringSync().contains('\r\n');
+  final bool useCRLF = projectDir.childFile('pubspec.yaml').readAsStringSync().contains('\r\n');
 
   LocalizationsGenerator generator;
   try {

packages/flutter_tools/test/general.shard/generate_localizations_test.dart

@@ -687,7 +687,41 @@ void main() {
   });
 
   group('generateLocalizations', () {
-    // Regression test for https://github.com/flutter/flutter/issues/119593
+    testWithoutContext('works even if CWD does not have a pubspec.yaml', () async {
+      final Directory projectDir = fs.currentDirectory.childDirectory('project')..createSync(recursive: true);
+      final Directory l10nDirectory = projectDir.childDirectory('lib').childDirectory('l10n')
+        ..createSync(recursive: true);
+      l10nDirectory.childFile(defaultTemplateArbFileName)
+        .writeAsStringSync(singleMessageArbFileString);
+      l10nDirectory.childFile(esArbFileName)
+        .writeAsStringSync(singleEsMessageArbFileString);
+      projectDir.childFile('pubspec.yaml')
+        ..createSync(recursive: true)
+        ..writeAsStringSync('''
+flutter:
+  generate: true
+''');
+
+      final Logger logger = BufferLogger.test();
+      logger.printError('An error output from a different tool in flutter_tools');
+
+      // Should run without error.
+      await generateLocalizations(
+        fileSystem: fs,
+        options: LocalizationOptions(
+          arbDir: Uri.directory(defaultL10nPathString).path,
+          outputDir: Uri.directory(defaultL10nPathString, windows: false).path,
+          templateArbFile: Uri.file(defaultTemplateArbFileName, windows: false).path,
+          syntheticPackage: false,
+        ),
+        logger: logger,
+        projectDir: projectDir,
+        dependenciesDir: fs.currentDirectory,
+        artifacts: artifacts,
+        processManager: processManager,
+      );
+    });
+
     testWithoutContext('other logs from flutter_tools does not affect gen-l10n', () async {
       _standardFlutterDirectoryL10nSetup(fs);