gn: fix bootstrap on windows

Review-Url: https://codereview.chromium.org/2883473002
Cr-Original-Commit-Position: refs/heads/master@{#471320}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: dfb837a97c2ee14bbcfb04a8bdd1a23813cab054
1 file changed
tree: 800671de1db981c6371b5656d19b8f9b78601780
  1. tools/