Michel Dänzer authored Dec 17, 2020 and Michel Dänzer committed Jan 22, 2021

While this isn't critical yet, it might become so at some point, so
let's make sure it keeps working.

Don't set the PIGLIT/XTEST_DIR variables for ninja dist, testing XTS
once against each DDX is enough (as part of ninja test).

Requires git in the docker image.

v2:
* Drop /usr/local/bin/xkbcomp symlink, no longer needed with xkbcomp
  1.4.1 (Peter Hutterer)