Always create output_dir before invoking gtest-parallel.

TBR=phoglund@webrtc.org

Bug: None
Change-Id: I7c62da5d4c65e6d9e7ab9caf99c84f28f669c739
Reviewed-on: https://webrtc-review.googlesource.com/54422
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22077}

tools_webrtc/gtest-parallel-wrapper.py

@@ -169,6 +169,9 @@ def main():
       gtest_parallel_path,
   ] + args.gtest_parallel_args
 
+  if args.output_dir and not os.path.isdir(args.output_dir):
+    os.makedirs(args.output_dir)
+
   print 'gtest-parallel-wrapper: Executing command %s' % ' '.join(command)
   sys.stdout.flush()