Print the name of the auto-detected gn build when running tests

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 425 matching lines @@
     latest_timestamp = -1
     latest_config = None
     for gn_config in os.listdir(gn_out_dir):
       gn_config_dir = os.path.join(gn_out_dir, gn_config)
       if not isdir(gn_config_dir):
         continue
       if os.path.getmtime(gn_config_dir) > latest_timestamp:
         latest_timestamp = os.path.getmtime(gn_config_dir)
         latest_config = gn_config
     if latest_config:
+      print(">>> Latest GN build found is %s" % latest_config)
       options.outdir = os.path.join(DEFAULT_OUT_GN, latest_config)
 
   build_config_path = os.path.join(
       BASE_DIR, options.outdir, "v8_build_config.json")
   if os.path.exists(build_config_path):
     try:
       with open(build_config_path) as f:
         build_config = json.load(f)
     except Exception:
       print ("%s exists but contains invalid json. Is your build up-to-date?" %
@@ skipping 441 matching lines @@
         "--coverage-dir=%s" % options.sancov_dir])
     except:
       print >> sys.stderr, "Error: Merging sancov files failed."
       exit_code = 1
 
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())