Change how MB handles goma_dir.

Change how MB handles goma_dir.

Since both GN and GYP actually have two settings for
whether to use GOMA and where to find it, it turns
out that you can and should set goma_dir independently
of what is actually specified in the MB configs (or iOS
configs): if MB specifies --goma-dir, then explicitly
set goma_dir, else don't set it at all.

This simplifies the code a bit and will solve a problem
in GN down the road as we switch to using args files.

R=brettw@chromium.org
BUG=602528
Committed: https://crrev.com/d0c138bb06b285b4ad0015f2fff407f5840e481e
Cr-Commit-Position: refs/heads/master@{#387038}

[Dirk Pranke, 2016-04-12 18:03:20]

https://codereview.chromium.org/1877173002/diff/1/tools/mb/mb.py
File tools/mb/mb.py (right):

https://codereview.chromium.org/1877173002/diff/1/tools/mb/mb.py#newcode855
tools/mb/mb.py:855: gn_args += ' goma_dir="%s"' % self.args.goma_dir
Ideally gn_args and gyp_defines would be lists of key=value strings, but in
order 
to get that I'd need to rewrite all of the entries in mb_config.pyl, which I
don't 
want to do as part of this series of patches.

[brettw, 2016-04-12 21:48:20]

lgtm

[Dirk Pranke, 2016-04-13 16:27:48]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2016-04-13 16:28:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1877173002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1877173002/1

[commit-bot: I haz the power, 2016-04-13 18:28:59]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-13 18:29:58]

Description was changed from

==========
Change how MB handles goma_dir.

Since both GN and GYP actually have two settings for
whether to use GOMA and where to find it, it turns
out that you can and should set goma_dir independently
of what is actually specified in the MB configs (or iOS
configs): if MB specifies --goma-dir, then explicitly
set goma_dir, else don't set it at all.

This simplifies the code a bit and will solve a problem
in GN down the road as we switch to using args files.

R=brettw@chromium.org
BUG=602528
==========

to

==========
Change how MB handles goma_dir.

Since both GN and GYP actually have two settings for
whether to use GOMA and where to find it, it turns
out that you can and should set goma_dir independently
of what is actually specified in the MB configs (or iOS
configs): if MB specifies --goma-dir, then explicitly
set goma_dir, else don't set it at all.

This simplifies the code a bit and will solve a problem
in GN down the road as we switch to using args files.

R=brettw@chromium.org
BUG=602528

Committed: https://crrev.com/d0c138bb06b285b4ad0015f2fff407f5840e481e
Cr-Commit-Position: refs/heads/master@{#387038}
==========

[commit-bot: I haz the power, 2016-04-13 18:29:59]

Patchset 1 (id:??) landed as
https://crrev.com/d0c138bb06b285b4ad0015f2fff407f5840e481e
Cr-Commit-Position: refs/heads/master@{#387038}