win: Use ninja by default

win: Use ninja by default

With this change, `gclient runhooks` creates ninja files by default on
Windows. To build, run `ninja -C out\Release chrome`. The output appears
in out\ instead of build\.

If you need to use a VS build for some reason, you can still
`set GYP_GENERATORS=msvs`. This is no longer a tested configuration.

Bots should automatically pick up the binaries in the new location (out).
If something does break, it should be safe to revert this change, and bots
should then automatically go back to picking up binaries from the old
location (build).

R=thakis@chromium.org
BUG=303291
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243782

[scottmg, 2014-01-07 18:17:01]

As mentioned, the trybots are useless, but I guess they check the code is
syntactically correct.

chrome-pmo@ has been pinged, and said "the sooner the better".

[Nico, 2014-01-07 18:43:45]

lgtm

I was idly thinking about adding a win_msvs trybot that uses msvs so that we
could trybot this, but since it's safe to revert, might as well see what happens
:-)

[scottmg, 2014-01-09 05:08:53]

Committed patchset #1 manually as r243782 (presubmit successful).