This sketches out what a world without Chrome's GN configs would look like.
Instead of DEPSing in build/, we now host our own gypi_to_gn.py.
The symlink from skia/ to . lets us run gclient hooks when the .gclient file is in the directory above skia/ or inside skia/. That means we don't need gn.py anymore.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2167163002
Review-Url: https://codereview.chromium.org/2167163002
