[libc++] Escape spaces in GoogleBenchmark microbenchmarks

Otherwise we generate data that isn't valid according to
the LNT format.

Author: ldionne

libcxx/utils/parse-google-benchmark-results

@@ -41,7 +41,10 @@ def main(argv):
         benchmark = headers.index('Benchmark')
         time = headers.index(args.timing)
         for row in rows:
-            print(f'{row[benchmark].replace(".", "_")}.execution_time {row[time]}')
+            # LNT format uses '.' to separate the benchmark name from the metric, and ' '
+            # to separate the benchmark name + metric from the numerical value. Escape both.
+            escaped = row[benchmark].replace(".", "_").replace(" ", "_")
+            print(f'{escaped}.execution_time {row[time]}')
 
 if __name__ == '__main__':
     main(sys.argv[1:])