Enable PPC64LE target
We should enable the ppc64le target, so as to more quickly discover future compile regressions.
I've built and tested on a local ppc64le VM. I was also able to build on Copr, both for Fedora 30 and Rawhide.
If this patch is accepted, then the official @kicad Copr should also be modified to include ppc64le as a build target.