GN Windows build fixes

GN Windows build fixes

Most importantly, this passes cflags_cc to the C++ compiler.

This fixes some flag differences with the GYP build, especially when running on 64 bit.

It disables a TLS test on static debug x64 builds which also fails in GYP. This configuration is not run on the bots but is the standard GN Windows build.

BUG=251251
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:android_chromium_gn_compile_dbg,android_chromium_gn_compile_rel;tryserver.chromium.win:win8_chromium_gn_rel,win8_chromium_gn_dbg;tryserver.chromium.mac:mac_chromium_gn_rel,mac_chromium_gn_dbg

Committed: https://crrev.com/9a19ddbe04e2be759a15c6a70f6585152611af23
Cr-Commit-Position: refs/heads/master@{#326856}

[brettw, 2015-04-20 22:24:49]

brettw@chromium.org changed reviewers:
+ scottmg@chromium.org

[scottmg, 2015-04-20 22:26:23]

lgtm

[scottmg, 2015-04-20 22:26:35]

BUG=251251

[brettw, 2015-04-21 16:39:38]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-04-21 16:40:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1062743005/1

[brettw, 2015-04-21 16:43:05]

The CQ bit was unchecked by brettw@chromium.org

[brettw, 2015-04-21 16:43:19]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-04-21 16:43:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1062743005/1

[brettw, 2015-04-21 17:23:49]

The CQ bit was unchecked by brettw@chromium.org

[brettw, 2015-04-24 18:12:31]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-04-24 18:12:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1062743005/1

[brettw, 2015-04-24 18:13:21]

The CQ bit was unchecked by brettw@chromium.org

[brettw, 2015-04-24 18:14:07]

The CQ bit was checked by brettw@chromium.org

[brettw, 2015-04-24 18:14:08]

The patchset sent to the CQ was uploaded after l-g-t-m from scottmg@chromium.org
Link to the patchset: https://codereview.chromium.org/1062743005/#ps20001
(title: "merge")

[commit-bot: I haz the power, 2015-04-24 18:15:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1062743005/20001

[commit-bot: I haz the power, 2015-04-24 19:31:00]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-24 19:31:43]

Patchset 2 (id:??) landed as
https://crrev.com/9a19ddbe04e2be759a15c6a70f6585152611af23
Cr-Commit-Position: refs/heads/master@{#326856}