This prepares for pulling chromium's build as dependency for
gn. After this, the files in build and gypfiles need to stay
in sync until chromium is updated.
BUG=chromium:474921
LOG=n
Review-Url: https://codereview.chromium.org/1848553003
Cr-Commit-Position: refs/heads/master@{#35898}
This also ports a few changes from run-test.py to make sure
cwd = v8 root directory.
BUG=chromium:535160
LOG=n
Review URL: https://codereview.chromium.org/1707963003
Cr-Commit-Position: refs/heads/master@{#34110}