Merge remote-tracking branch 'origin/deploy' into deploy.gibson

* origin/deploy:
  Makefile: Don't insist on `/usr/lib/.../coreutils/'.
  bin/chroot-maint: Enhance the `CROSS_TOOLS' pattern machinery.
  Makefile: Include C++ headers in the cross-tools bundle.
  Makefile: Use buster's Qemu on stretch.
  Makefile, bin/chroot-maint: Allow source distribution selection for Qemu.
  bin/chroot-maint: Add missing format argument to diagnostic.