Do not delete temporary directory if user specified it manually.

webrtc/examples/androidtests/gradle_project_test.py

 #!/usr/bin/env python
 # Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 """
@@ skipping 49 matching lines @@
   output_dir = os.path.abspath(args.build_dir_android)
   project_dir = os.path.abspath(project_dir)
 
   try:
     _RunCommand([GENERATE_GRADLE_SCRIPT, '--output-directory', output_dir,
         '--target', '//webrtc/examples:AppRTCMobile',
         '--project-dir', project_dir,
         '--use-gradle-process-resources', '--split-projects'])
     _RunCommand([GRADLEW_BIN, 'assembleDebug'], project_dir)
   finally:
-    shutil.rmtree(project_dir, True)
+    # Do not delete temporary directory if user specified it manually.
+    if not args.project_dir:
+      shutil.rmtree(project_dir, True)
 
 
 if __name__ == '__main__':
   sys.exit(main())