GN: Look at all target outputs when detecting duplicates

BUG=554660

Review URL: https://codereview.chromium.org/1828113002

Cr-Original-Commit-Position: refs/heads/master@{#384357}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 83671be906e98ac69bbfaf2c2206977806ff5448
4 files changed
tree: b13667fe0466353a0fada174e8df77febed8bd9c
  1. tools/