Restore logic to check for .git in ANGLE BUILD.gn

This should ensure that for users where the ANGLE git repo is present,
we correctly re-generate commit.h when rolling to a new revision.

Cq-Include-Trybots: skia/skia.primary:Build-Debian9-Clang-x86_64-Release-ANGLE;skia/skia.primary:Test-Win10-Clang-AlphaR2-GPU-RadeonR9M470X-x86_64-Debug-All-ANGLE;skia/skia.primary:Test-Win10-Clang-Golo-GPU-QuadroP400-x86_64-Debug-All-ANGLE;skia/skia.primary:Test-Win10-Clang-NUC5i7RYH-GPU-IntelIris6100-x86_64-Debug-All-ANGLE;skia/skia.primary:Test-Win10-Clang-NUC6i5SYK-GPU-IntelIris540-x86_64-Debug-All-ANGLE;skia/skia.primary:Test-Win10-Clang-NUC8i5BEK-GPU-IntelIris655-x86_64-Debug-All-ANGLE;skia/skia.primary:Test-Win10-Clang-NUCD34010WYKH-GPU-IntelHD4400-x86_64-Debug-All-ANGLE
Change-Id: Ib3c77a19d243896f4e7359dc4f14e87d4907739e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/274498
Reviewed-by: Geoff Lang <geofflang@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed