BUG=

Review-Url: https://codereview.chromium.org/2126423002
Cr-Commit-Position: refs/heads/master@{#37600}

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}

BUG=chromium:515782
LOG=n

Review URL: https://codereview.chromium.org/1273403002

Cr-Commit-Position: refs/heads/master@{#30056}

BUG=v8:3880
LOG=n
TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/908173002

Cr-Commit-Position: refs/heads/master@{#26537}

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}