Recent changes in grub added a new command option to fwsetup and changed the
way the command is invoked in the generated boot configuration. Depending on
your system hardware and setup this could cause an unbootable system due to
incompatibilities between the installed bootloader and configuration. After a
grub package update it is advised to run both, installation and regeneration
of configuration:
grub-install ...
grub-mkconfig -o /boot/grub/grub.cfg
For more specific information on grub-install, please refer to the wiki:
GRUB - ArchWiki