GN: compiler_prefix -> cc_wrapper

I was a bit mixed up thinking Chrome called this feature compiler_prefix.
They actually call it cc_wrapper.  So let's switch to their name before we
get too used to this.

No bots are affected.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2355003002
DOCS_PREVIEW= https://skia.org/?cl=2355003002

NOTREECHECKS=true

Review-Url: https://codereview.chromium.org/2355003002
2 files changed