Add avx2 sources to GN build file

Add avx2 sources to GN build file

TBR=tomfinegan@chromium.org

Committed: 11ade561de716842ba299f11900490d293a44fcd

[Johann, 2015-01-22 17:04:36]

Committed patchset #1 (id:1) manually as
11ade561de716842ba299f11900490d293a44fcd (presubmit successful).

[Johann, 2015-01-22 17:18:21]

johannkoenig@google.com changed reviewers:
+ ckocagil@chromium.org

[Johann, 2015-01-22 17:18:22]

Cem, you touched some of the GN files here:
https://codereview.chromium.org/603173004/

Specifically, you fixed some Windows issues. Any ideas on how to pass /arch:AVX2
(or EnableEnhancedInstructionSet': '3', # /arch:AVX as we use in
libvpx_srcs_x86_intrinsics.gypi) through GN?

Roll:
https://codereview.chromium.org/845453005/
and failure:
http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_gn_...

I'm having trouble setting up a local GN build, and committing/rolling->trybots
isn't exactly the best way to sort through this.

[Tom Finegan, 2015-01-22 17:33:59]

On 2015/01/22 17:18:22, Johann wrote:
> Cem, you touched some of the GN files here:
> https://codereview.chromium.org/603173004/
> 
> Specifically, you fixed some Windows issues. Any ideas on how to pass
/arch:AVX2
> (or EnableEnhancedInstructionSet': '3', # /arch:AVX as we use in
> libvpx_srcs_x86_intrinsics.gypi) through GN?
> 
> Roll:
> https://codereview.chromium.org/845453005/
> and failure:
>
http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_gn_...
> 
> I'm having trouble setting up a local GN build, and
committing/rolling->trybots
> isn't exactly the best way to sort through this.

lgtm

[ckocagil, 2015-01-22 18:25:14]

https://codereview.chromium.org/865893004/diff/1/BUILD.gn
File BUILD.gn (right):

https://codereview.chromium.org/865893004/diff/1/BUILD.gn#newcode135
BUILD.gn:135: cflags = [ "-mavx2" ]
This should be:

  if (is_win) {
    cflags = [ "/arch:AVX" ]
  } else {
    cflags = [ "-mavx2" ]
  }