Release 1.48.0

Feature:
* pmb.chroot.root: set PYTHONUNBUFFERED=1 (MR 2209)

Fixes:
* pmb.build._package: update isl workaround (MR 2213)

Other:
* pmb.chroot.root: order env vars alphabetically (MR 2209)
* pmb.aportgen.device: no depend on mesa-dri-gallium (MR 2210)