Add back /usr/bin/cc (symlink to gcc) as some build step actually calls that explicitly

Change-Id: I20d07d67e7313d420d7f9b5c473faf6c158c92e3
Reviewed-on: http://review.couchbase.org/40819
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>