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}
Also enabled concurrent linking with gold on Linux.
Mostly copy and paste from Chromium with customization for
V8 where necessary.
BUG=v8:3880
LOG=n
Review URL: https://codereview.chromium.org/896703003
Cr-Commit-Position: refs/heads/master@{#26536}