GN: turn off ccache

GN: turn off ccache

I just burned 2 days debugging a confusing interaction between ccache
and the -fsanitize-blacklist argument to Clang.  Let's see if we can
live without ccache (swarming affinity + Ninja seems pretty decent).

As a point of reference, the Mac bots have been looking for ccache but
failing to find it.  They're proof this will be fine.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2310063003

Review-Url: https://codereview.chromium.org/2310063003