* util/update-grub_lib.in (convert_system_path_to_grub_path): Abort if
file doesn't exist, or if it is in a filesystem grub can't read.
* util/update-grub.in: Set fallback for GRUB_FS check to "unknown". Do
not abort if GRUB_DRIVE could not be defined. Rearrange generated
header comment to fit in 80 columns when the variables are resolved.
* util/grub.d/00_header.in: Only set root variable when GRUB_DRIVE
could be identified by update-grub. Remove redundant check for
unifont.pff existance (since convert_system_path_to_grub_path now
handles that).
c0f90770b8