Ensure all test targets are built on Android.

Ensure all test targets are built on Android.

When GYP runs for OS=android it doesn't generate the
video_engine_core_unittests_apk_target target which is needed to
get the APK built.
The same problem applies to webrtc/test/webrtc_test_common.gyp,
but that unittest is not added on any bot anyway, so that's future work.

TESTED=Ran webrtc/build/gyp_webrtc for Linux and Android locally.
Before this patch, the video_engine_core_unittests was not built
as part of the 'All' target. With this patch, it is now built.

R=pbos@webrtc.org

Committed: https://crrev.com/afb6b5e3e0a2d7040e183d09e40071074017c0ad
Cr-Commit-Position: refs/heads/master@{#9952}

[kjellander_webrtc, 2015-09-16 11:54:34]

kjellander@webrtc.org changed reviewers:
+ pbos@webrtc.org

[pbos-webrtc, 2015-09-16 12:05:06]

lgtm assuming no platforms complain w/r/t circular dependencies or something
like that (please CQ) :)

[kjellander_webrtc, 2015-09-16 12:07:51]

Committed patchset #1 (id:1) manually as
afb6b5e3e0a2d7040e183d09e40071074017c0ad (presubmit successful).

[commit-bot: I haz the power, 2015-09-16 12:07:52]

Patchset 1 (id:??) landed as
https://crrev.com/afb6b5e3e0a2d7040e183d09e40071074017c0ad
Cr-Commit-Position: refs/heads/master@{#9952}

[kjellander_webrtc, 2015-09-16 12:19:01]

On 2015/09/16 12:05:06, pbos-webrtc wrote:
> lgtm assuming no platforms complain w/r/t circular dependencies or something
> like that (please CQ) :)

Since we don't use the circular dependencies detection (unfortunately, see
https://code.google.com/p/webrtc/issues/detail?id=4243) there's no risk for
that.
I wanted to get this in to unblock the CQ as I clobbered one of the bots
earlier, causing it to start failing on every build.

Seems like this landed nicely on the bots.