Make gyp_flag_compare.py work on Windows

BUG=

Review URL: https://codereview.chromium.org/1319063004

Cr-Original-Commit-Position: refs/heads/master@{#348113}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d9838e11893e2f80ae1d0d25dd9e8d6c41697f79
1 file changed
tree: 5e64fec64684e3703d3b949b835adf96003587e8
  1. tools/