If :builtin matches do not execute :build/:info.

Currently :build/:info properties are executed even if a package is
builtin.  This however is due to fail because the normal method is
being replaced.

Therefore if :type is 'builtin *and* the recipe has a :builtin
property neither :build nor :info are executed.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Recipe: builtin since 24.3

"Since version 24.3 of Emacs, RefTeX is developed exclusively as part
of Emacs."

https://www.gnu.org/software/auctex/reftex.html
Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Merge pull request #1221 from ruediger/builtin-build

If :builtin matches do not execute :build/:info.