build: Add libffi as a build dependency on linux.

build: Add libffi as a build dependency on linux.

libffi is already a run-time dependency as libgobject depends on it.

BUG=549782
Committed: https://crrev.com/dd26069ac26c43fcb8628e61eb6d45cc1f696f01
Cr-Commit-Position: refs/heads/master@{#358662}

[reveman, 2015-11-09 18:05:59]

The CQ bit was checked by reveman@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-11-09 18:07:16]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410093009/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410093009/1

[commit-bot: I haz the power, 2015-11-09 18:18:09]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-09 18:18:10]

Dry run: This issue passed the CQ dry run.

[reveman, 2015-11-09 19:28:48]

reveman@chromium.org changed reviewers:
+ thakis@chromium.org

[Nico, 2015-11-09 21:21:51]

lgtm

[reveman, 2015-11-09 21:28:08]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2015-11-09 21:29:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410093009/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410093009/1

[commit-bot: I haz the power, 2015-11-09 21:39:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-09 21:40:26]

Patchset 1 (id:??) landed as
https://crrev.com/dd26069ac26c43fcb8628e61eb6d45cc1f696f01
Cr-Commit-Position: refs/heads/master@{#358662}