gyp: use all processors instead of hard-coded 8

gyp: use all processors instead of hard-coded 8.

Makes no difference for me but might help others because gyp can easily
keep lots of processors busy.

BUG=362075
Originally landed at r1896 and backed out at r1911. This should be safe
to land after r1913.

Patch by Daniel Bratell <bratell@opera.com>;.

R=torne@chromium.org

Committed: https://code.google.com/p/gyp/source/detail?r=1928

[Daniel Bratell, 2014-06-05 06:52:06]

On 2014/05/06 17:59:00, Mark Mentovai wrote:

I shouldn't say L G T M to my own patch, should I? Or should I just do that
anyway just to make the systems happy. It was reviewed ok last time after all.

[Torne, 2014-06-05 09:28:48]

LGTM

[Mark Mentovai, 2014-06-05 13:27:46]

Committed patchset #1 manually as r1928 (presubmit successful).