MIPS: added --mips-arch-variant option to test.py.

MIPS: added --mips-arch-variant option to test.py.


BUG=
TEST=

Committed: https://code.google.com/p/v8/source/detail?r=10497

[Jakob Kummerow, 2012-01-20 14:24:50]

Drive-by comment:
Building with SCons (which is what test.py dispatches to) will soon be
deprecated. In the future, the only supported way to build V8 will be the
GYP-based build, which doesn't know the MIPS arch variant flag at all yet. If
you want this flag to still be available, you should add it to the gyp build
(preferably to build/common.gypi, and to the top-level Makefile).

[danno, 2012-01-25 12:35:03]

LGTM, landing.