Update documentation links to GN quickstart.

Bug: 859536
Change-Id: I3cba0cfe960917dd87eff238ea9d6a11e5dc88ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1783662
Auto-Submit: Eric Roman <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Commit-Queue: Nico Weber <[email protected]>
Cr-Commit-Position: refs/heads/master@{#692919}
5 files changed