libsdl2-dev does not depend on libpng-dev and libjpeg-dev,
so add those to build-deps or else build fails

Use the python:any syntax to pull build version of
python when cross-building qemu.

Enable building for arm64; the arm64 target is not yet merged, but the package doesn't need arm64 target support to build for an arm64 host.

Enable building for ppc64el (in both Debian and Ubuntu): Debian does not have a ppc64el port yet, but qemu builds out of the box there so it's safe/appropriate to enable.

This reverts commit 5dcf8dcb.
Apparently the archive isn't ready for foo:any build-depends yet.

Use the python:any syntax to pull build version of
python when cross-building qemu.