sync: Separate .gyp file for standalone tools

sync: Separate .gyp file for standalone tools

Moves targets related to the standalone executables
sync_listen_notifications and sync_client into their own .gyp file.

This will prevent a temporary circular dependency as we attempt to
invert the dependency from components/invalidation -> sync towards
sync -> components/invalidation.

BUG=378024
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=273665

[rlarocque, 2014-05-28 19:40:06]

I think this fixes the circular dependency that is currently blocking
https://codereview.chromium.org/294123004/.

Please review.

[rlarocque, 2014-05-28 20:47:18]

Updated as discussed.

[maniscalco, 2014-05-29 21:46:53]

lgtm

[rlarocque, 2014-05-29 21:51:44]

The CQ bit was checked by rlarocque@chromium.org

[commit-bot: I haz the power, 2014-05-29 21:52:47]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rlarocque@chromium.org/303603004/40001

[commit-bot: I haz the power, 2014-05-29 22:37:35]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered...)

[commit-bot: I haz the power, 2014-05-29 23:47:13]

Change committed as 273665