CMake: exclude SkOSLibrary_posix.cpp on Windows too.

CMake: exclude SkOSLibrary_posix.cpp on Windows too.

BUG=skia:
CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Release-CMake-Trybot,Build-Mac10.9-Clang-x86_64-Release-CMake-Trybot

Committed: https://skia.googlesource.com/skia/+/e092cee9ad96c8df1af05dcb0c078874b67c1a8e

[mtklein_C, 2015-10-26 14:59:31]

mtklein@chromium.org changed reviewers:
+ marco.diiga@gmail.com

[mtklein_C, 2015-10-26 14:59:36]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-26 14:59:47]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1414983004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1414983004/1

[commit-bot: I haz the power, 2015-10-26 15:16:52]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-26 15:16:53]

Dry run: This issue passed the CQ dry run.

[Marco A., 2015-10-26 15:38:33]

lgtm

Works for me. Lgtm!

[mtklein, 2015-10-26 15:40:13]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-10-26 15:40:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1414983004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1414983004/1

[commit-bot: I haz the power, 2015-10-26 15:41:12]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/e092cee9ad96c8df1af05dcb0c078874b67c1a8e