GN: Don't build dist_jar for _incremental targets

GN: Don't build dist_jar for _incremental targets

It may actually turn out that dist_jar is necessary for tests, but for now
*_incremental apks don't work for tests anyways, and building dist_jar
slows down the build.

BUG=533442
Committed: https://crrev.com/aad19dc0d13604a8e7009dffc2608822fe1a7f4d
Cr-Commit-Position: refs/heads/master@{#350456}

[agrieve, 2015-09-23 18:02:31]

agrieve@chromium.org changed reviewers:
+ pkotwicz@chromium.org

[pkotwicz, 2015-09-23 18:14:50]

lgtm

[agrieve, 2015-09-24 02:24:35]

The CQ bit was checked by agrieve@chromium.org

[commit-bot: I haz the power, 2015-09-24 02:26:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1362743004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1362743004/1

[commit-bot: I haz the power, 2015-09-24 03:00:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-24 03:01:24]

Patchset 1 (id:??) landed as
https://crrev.com/aad19dc0d13604a8e7009dffc2608822fe1a7f4d
Cr-Commit-Position: refs/heads/master@{#350456}