grub-1.98-r1: make: *** No rule to make target `ascii.h', needed by `font_mod-font_font.o'

しばらく前からこんなエラーが出てて、sys-boot/grub-1.98 がアップデートできなかった。

x86_64-pc-linux-gnu-gcc -Ifont -I./font -nostdinc -isystem /usr/lib/gcc/x86_64-pc-linux-gnu/4.4.3/include -I./include -I. -I./include -Wall -W  -Os -DGRUB_MACHINE_PCBIOS=1 -Wall -W -Wshadow -Wpointer-arith -Wmissing-prototypes                -Wundef -Wstrict-prototypes -g -falign-jumps=1 -falign-loops=1 -falign-functions=1 -mno-mmx -mno-sse -mno-sse2 -mno-3dnow -fno-dwarf2-cfi-asm -m32 -fno-stack-protector -mno-stack-arg-probe -fno-builtin -mrtd -mregparm=3 -m32 -MD -c -o font_mod-font_font_cmd.o font/font_cmd.c
make: *** No rule to make target `ascii.h', needed by `font_mod-font_font.o'.  Stop.
 * ERROR: sys-boot/grub-1.98-r1 failed:
 *   making regular stuff
 * 
 * Call stack:
 *     ebuild.sh, line  47:  Called src_compile
 *   environment, line 3236:  Called die
 * The specific snippet of code:
 *       emake -j1 || die "making regular stuff"
 * 
 * If you need support, post the output of 'emerge --info =sys-boot/grub-1.98-r1',
 * the complete build log and the output of 'emerge -pqv =sys-boot/grub-1.98-r1'.
 * The complete build log is located at '/var/tmp/portage/sys-boot/grub-1.98-r1/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-boot/grub-1.98-r1/temp/environment'.
 * S: '/var/tmp/portage/sys-boot/grub-1.98-r1/work/grub-1.98'

>>> Failed to emerge sys-boot/grub-1.98-r1, Log file:

>>>  '/var/tmp/portage/sys-boot/grub-1.98-r1/temp/build.log'

そのうち直るだろうと思って放置してたけれど、数ヶ月経過しても改善されないのでググってみたところ、
これが該当。

USE Flag に mkfont をいれたら問題なくコンパイルが通るようになった。