This is probably related to http://git.savannah.gnu.org/cgit/grub.git/commit/?id=26031d3b101648352e4e427f04bf69d320088e77 - if the config change from that commit is combined with an older grub2 binary, the binary will interpret `fwsetup --is-supported` as `fwsetup` and immediately reboot into the BIOS setup.
This will happen when loading a new config from an old grub2, like the one bundled with the Debian installer ISO/USB. This also happens with the grub2 binary that's part of the 2.12~rc1-12 package - maybe it wasn't cleanly compiled? Or I have some older files installed somewhere?!
