libcxx: fix merge_archives error variable name

Differential Revision: https://reviews.llvm.org/D37728

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@313084 91177308-0d34-0410-b5e6-96231b3b80d8

utils/merge_archives.py

@@ -120,7 +120,7 @@ def main():
 
     files = glob.glob(os.path.join(temp_directory_root, '*.o*'))
     if not files:
-        print_and_exit('Failed to glob for %s' % glob_path)
+        print_and_exit('Failed to glob for %s' % temp_directory_root)
     cmd = [ar_exe, '-qc', args.output] + files
     execute_command_verbose(cmd, cwd=temp_directory_root, verbose=args.verbose)