[linux] Improve link time with Chromium-bundled binutils.

[linux] Improve link time with Chromium-bundled binutils.

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

Committed: https://crrev.com/e06dc0569a01cff00cd8d726457015182bea8f98
Cr-Commit-Position: refs/heads/master@{#26536}

[Benedikt Meurer, 2015-02-10 07:22:13]

bmeurer@chromium.org changed reviewers:
+ svenpanne@chromium.org

[Benedikt Meurer, 2015-02-10 07:22:14]

PTAL

[Sven Panne, 2015-02-10 07:25:27]

LGTM (mostly rubber-stamped)

[Benedikt Meurer, 2015-02-10 07:25:36]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-02-10 07:26:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/896703003/20001

[commit-bot: I haz the power, 2015-02-10 07:27:10]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-10 07:27:26]

Patchset 2 (id:??) landed as
https://crrev.com/e06dc0569a01cff00cd8d726457015182bea8f98
Cr-Commit-Position: refs/heads/master@{#26536}