gitignore: ignore config.cache-env

Summary: like config.cache, this should also be ignored.

Reviewers: billiob

Differential Revision: https://phab.enlightenment.org/D1300
autotools: we don't need to repeat ourselves

Reviewers: billiob

Differential Revision: https://phab.enlightenment.org/D1301
autotools: Fix MAINTAINERCLEAN rules

Summary:
We do not ship a .tar.bz2 but a tar.xz, thus we have to clean the
later.

Reviewers: billiob

Differential Revision: https://phab.enlightenment.org/D1302