fix the zip tool when building for ios

packages/flutter_tools/lib/src/zip.dart

@@ -91,17 +91,22 @@ class _ZipToolBuilder extends ZipBuilder {
       }
     }
 
+    if (_getCompressedNames().isNotEmpty) {
       runCheckedSync(
         <String>['zip', '-q', outFile.absolute.path]..addAll(_getCompressedNames()),
         workingDirectory: zipBuildDir.path,
         truncateCommand: true
       );
+    }
+
+    if (_getStoredNames().isNotEmpty) {
       runCheckedSync(
         <String>['zip', '-q', '-0', outFile.absolute.path]..addAll(_getStoredNames()),
         workingDirectory: zipBuildDir.path,
         truncateCommand: true
       );
     }
+  }
 
   Iterable<String> _getCompressedNames() {
     return entries