gn: fix bootstrap.py after https://codereview.chromium.org/2846893003

BUG=none

Review-Url: https://codereview.chromium.org/2860753004
Cr-Original-Commit-Position: refs/heads/master@{#469332}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 643d6bc90fead3ccefa9309d265dd048e51c263f
1 file changed
tree: 905ef96bb678786d3f4f20fd15dc4491a44ab3a4
  1. tools/