Improve Windows GN build setup.

Improve Windows GN build setup.

Properly setup a new output build directory on Windows (previously you had to manually copy some files into it). It now creates the environment block and the gyp-win-tool.

The include and library paths are moved to the command line and removed from the environment which is cleaner and more explicit.

BUG=
R=scottmg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=230223

[scottmg, 2013-10-22 20:50:20]

this won't work for the x64 toolchain because the PATH has to be different to
load the x64 dlls?

[brettw, 2013-10-22 20:51:27]

On 2013/10/22 20:50:20, scottmg wrote:
> this won't work for the x64 toolchain because the PATH has to be different to
> load the x64 dlls?

Poop!

[brettw, 2013-10-22 21:15:43]

Okay, I renamed the environment file to environment.x86. I don't do the x64 one
since that build doesn't work yet.

[scottmg, 2013-10-22 21:20:00]

lgtm

[brettw, 2013-10-22 22:03:50]

Committed patchset #3 manually as r230223 (presubmit successful).