Update to efibootmgr 15
- Make efibootmgr use EFIDIR / efibootmgr.efidir like fwupdate does
- make --loader default build-time configurable
- sanitize set_mirror()/get_mirror()
- Add support for parsing loader options as UCS2
- GCC 7 fixes
- Don't use -fshort-wchar since we don't run on EFI machines.
Signed-off-by: Peter Jones <pjones@redhat.com>