Support UEFI. Right now a grub-mkrescue with UEFI support can boot Sortix. I need to switch to multiboot 2 as in #499 so the kernel knows it's UEFI and it needs to let user-space know through kernelinfo(2). AHCI in virtualbox doesn't work under UEFI because it wants to use the interrupt pin of the PCI device (APIC) rather than the interrupt line (set to 0xFF and changing it to a real IRQ doesn't work). This may be the case for other drivers as well (untested as of right now). Untested on other UEFI systems and virtual machines. Installation on UEFI systems should be handled as well. Research that. Build UEFI target modules for GRUB. Make sysinstall and disked do things right for UEFI. FAT support is probably needed for the boot partition.