GN: port a few missing Android bits from GYP.
GN: port a few missing Android bits from GYP.

The SK_GAMMA_ defines change text rendering on Android.
This is how they're set in GYP for Android... everyone else is default (sRGB).

Linking AndroidSkDebugToStdOut.o causes SkDebugf to go to both logcat and
stdout on Android.  Without it, it only goes to logcat.  The file has no effect
on non-Android platforms.

BUG=skia:

Review-Url: https://codereview.chromium.org/2323353002

google/skia,aosp-mirror/platform_external_skia,google/skia,HalCanary/skia-hc,rubenvb/skia,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,HalCanary/skia-hc,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,Hikari-no-Tenshi/android_external_skia,google/skia,rubenvb/skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,google/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,rubenvb/skia,google/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,google/skia,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia