Update gn bootstrap to build with latest libc++ roll

BUG=None
R=thakis

Change-Id: I03a73f62d6bf014de829f81864f66db076b3db08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2723278
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#858235}
GitOrigin-RevId: 9a6a070f5baf05aa65c0f59cd17f5ca2dc5b6a0a
2 files changed
tree: 3d7cda2403f027dc3d30dc9ee72057961f90ee3f
  1. bootstrap/
  2. tutorial/
  3. README.md
  4. roll_gn.py
README.md

GN now lives at https://gn.googlesource.com/.

To roll the latest version of GN into Chromium:

  1. Create a new Git branch.
  2. Run python tools/gn/roll_gn.py; this will modify //DEPS and //buildtools/DEPS to point to the most recent revision of GN and create a commit with a list of the changes included in the roll.
  3. Run git-cl upload to upload the commit as a change for review.

If you don't want to roll to the latest version, you can specify the SHA-1 to roll to use as an argument to the script, and it will be used instead.