Eliminate build differences in nacl gated on nacl_standalone.

Eliminate build differences in nacl gated on nacl_standalone.

We currently use nacl_standalone to gate two things:
- differing settings in the gyp build
- toggle the plugin

Keeping our settings in sync with chrome is a pseudo-circularity.
Additionally, we will temporarily want to use nacl's gyp build
to build a full IRT. This is not possible without using chrome's
build settings which are expected by ppapi modules to be injected
via -Icommon.gypi.

R=ncbray@chromium.org
BUG=http://code.google.com/p/nativeclient/issues/detail?id=2957
TEST=None

[bradn, 2012-08-12 21:46:23]

Ok, I think this is ready for review.
There's a small question around clang, but I'll chat with you in person for
that.