grub-mkrescue from at least sys-boot/grub-1.99* needs xorriso to be usable at all: $ LC_ALL="C" grub-mkrescue -o test.img Enabling BIOS support ... /bin/grub-mkrescue: line 306: xorriso: command not found
Just fyi, xorriso is part of dev-libs/libisoburn which is already in the tree
Dep added in 1.99 and live.