Android: configure use_system_zlib in zlib.gyp

Android: configure use_system_zlib in zlib.gyp

Currently third_party/zlib/zlib.gyp uses the system libz if:
  os_posix == 1 and OS != "mac" and OS != "ios" and OS != "openbsd"

I'm assuming that Android sets os_posix==1 and therefore this change is
a no-op. But it consolidates control of this variable in a single
location.

BUG=none

[klobag.chromium, 2012-08-03 23:11:57]

lgtm

https://chromiumcodereview.appspot.com/10837100/diff/1/build/common.gypi
File build/common.gypi (left):

https://chromiumcodereview.appspot.com/10837100/diff/1/build/common.gypi#oldc...
build/common.gypi:983: 'use_system_zlib%': 1,
I assume that you have changed zlib.gyp.

[agl, 2012-08-06 11:47:45]

https://chromiumcodereview.appspot.com/10837100/diff/1/build/common.gypi
File build/common.gypi (left):

https://chromiumcodereview.appspot.com/10837100/diff/1/build/common.gypi#oldc...
build/common.gypi:983: 'use_system_zlib%': 1,
On 2012/08/03 23:11:57, klobag.chromium wrote:
> I assume that you have changed zlib.gyp.

Not yet, but that's a future CL.

[commit-bot: I haz the power, 2012-08-06 11:47:55]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/agl@chromium.org/10837100/1

[commit-bot: I haz the power, 2012-08-06 12:07:32]

Try job failure for 10837100-1 (retry) on win for step "compile" (clobber
build).
It's a second try, previously, step "compile" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win&number...