Revert 12273 Use parallel builds in build_nexe.py even without goma
Revert 12273 Use parallel builds in build_nexe.py even without goma

Somewhat speculative, something in the nacl roll caused most windows builds on
chromium's main waterfall to time out repeatedly, presumably due to thrashing.

Examples:
http://build.chromium.org/p/chromium.win/builders/Win%20x64%20Builder%20%28dbg%29/builds/3361
http://build.chromium.org/p/chromium.win/builders/Win%20x64%20Builder%20%28dbg%29/builds/3362
http://build.chromium.org/p/chromium.win/builders/Win%20x64%20Builder%20%28dbg%29/builds/3363
http://build.chromium.org/p/chromium.win/builders/Win%20x64%20Builder%20%28dbg%29/builds/3364

> build_nexe.py has code to run builds in parallel, but it is only used
> when building with goma. It's useful even without goma, so use it.
> Limit the number of parallel builds to 8 (since there's no way for gyp
> to pass the concurrency limit from the build system to build_nexe.py,
> the default is chosen to be large enough to benefit users with big
> machines, but small enough not to completely choke small machines).
> 
> R=sbc@chromium.org, yanagisawa@chromium.org
> BUG= https://code.google.com/p/chromium/issues/detail?id=277813
> 
> Review URL: https://codereview.chromium.org/23645002

TBR=dschuff@chromium.org

Review URL: https://codereview.chromium.org/29313005

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12284 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client