Pull in GYP_LINK_CONCURRENCY=N support.

Pull in GYP_LINK_CONCURRENCY=N support.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/1a50651524128c0843575a764185c0c4c5e7ee6e

[mtklein, 2014-06-06 01:40:39]

We can now try fiddling with how many things to link at once by setting
GYP_LINK_CONCURRENCY in the environment when running ./gyp_skia.

[borenet, 2014-06-06 11:42:45]

https://codereview.chromium.org/315183003/diff/1/DEPS
File DEPS (right):

https://codereview.chromium.org/315183003/diff/1/DEPS#newcode11
DEPS:11: "third_party/externals/gyp" :
"https://chromium.googlesource.com/external/gyp.git@3917682",
I think you want 3917682a16d5c19ff3576a8be0ffdb3a332954b1, right?
https://chromium.googlesource.com/external/gyp/+/3917682a16d5c19ff3576a8be0ff...

[mtklein, 2014-06-06 14:02:10]

https://codereview.chromium.org/315183003/diff/1/DEPS
File DEPS (right):

https://codereview.chromium.org/315183003/diff/1/DEPS#newcode11
DEPS:11: "third_party/externals/gyp" :
"https://chromium.googlesource.com/external/gyp.git@3917682",
On 2014/06/06 11:42:45, borenet wrote:
> I think you want 3917682a16d5c19ff3576a8be0ffdb3a332954b1, right?
>
https://chromium.googlesource.com/external/gyp/+/3917682a16d5c19ff3576a8be0ff...

Sure.   Prefixes work fine, but of course the whole thing works.

[borenet, 2014-06-06 14:08:32]

LGTM

https://codereview.chromium.org/315183003/diff/1/DEPS
File DEPS (right):

https://codereview.chromium.org/315183003/diff/1/DEPS#newcode11
DEPS:11: "third_party/externals/gyp" :
"https://chromium.googlesource.com/external/gyp.git@3917682",
On 2014/06/06 14:02:10, mtklein wrote:
> On 2014/06/06 11:42:45, borenet wrote:
> > I think you want 3917682a16d5c19ff3576a8be0ffdb3a332954b1, right?
> >
>
https://chromium.googlesource.com/external/gyp/+/3917682a16d5c19ff3576a8be0ff...
> 
> Sure.   Prefixes work fine, but of course the whole thing works.

Actually, I didn't even notice that one was a prefix of the other.  I saw a
string of digits and assumed it was an svn revision.  I think I like using the
full hash in this file, but I don't have a good justification.

[mtklein, 2014-06-06 14:10:48]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-06-06 14:11:15]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/mtklein@chromium.org/315183003/20001

[commit-bot: I haz the power, 2014-06-06 14:37:50]

Change committed as 1a50651524128c0843575a764185c0c4c5e7ee6e