Add logger indent option and indent nested xcode command outputs (#7867)

* Add indent option to logger and indent non-flutter nested output

* Add a missed override

* Formatting
diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index 2129afb..f2a85ac 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart
@@ -166,10 +166,15 @@
   );
 
   if (result.exitCode != 0) {
-    if (result.stderr.isNotEmpty)
-      printStatus(result.stderr);
-    if (result.stdout.isNotEmpty)
-      printStatus(result.stdout);
+    printStatus('Failed to build iOS app');
+    if (result.stderr.isNotEmpty) {
+      printStatus('Error output from Xcode build:\n↳');
+      printStatus(result.stderr, indent: 4);
+    }
+    if (result.stdout.isNotEmpty) {
+      printStatus('Xcode\'s output:\n↳');
+      printStatus(result.stdout, indent: 4);
+    }
     return new XcodeBuildResult(
       success: false,
       stdout: result.stdout,