racy: change the racy API
racy: change the racy API

racy now implements hash.Hash which means there is really no need
to XOR stuff in the native rules land.

racy still keeps the global hashCache for the HashFiles method.

Unlike sha512.New(), racy.New() takes options, these options
can be used for making a whitelist of extensions to be hashed.

Signed-off-by: sevki <a0f1490a20d0211c997b44bc357e1972deab8ae3@sevki.org>

bldy/build,bldy/build,bldy/build,bldy/build