Support Xcode projects with no schemes (#11750)

diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index 3885332..e6460ae 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart
@@ -294,7 +294,6 @@
     'clean',
     'build',
     '-configuration', configuration,
-    '-scheme', scheme,
     'ONLY_ACTIVE_ARCH=YES',
   ];
 
@@ -306,6 +305,7 @@
     if (fs.path.extension(entity.path) == '.xcworkspace') {
       commands.addAll(<String>[
         '-workspace', fs.path.basename(entity.path),
+        '-scheme', scheme,
         "BUILD_DIR=${fs.path.absolute(getIosBuildDirectory())}",
       ]);
       break;