Created attachment 288743 [details] patch to ebuild grub2-install (and apparently grub2-mkrescue and grub2-mknetdir although I haven't used them) are platform, and for efi target cpu dependent. The current ebuild installs only the version for one of the platforms listed in GRUB_PLATFORMS. Attached is a patch that installs one version per platform of these scripts (and an elog improvement - but not one for grub2-install message which I guess would be needed with this patch). Inspired by Arch Linux who create grub_bios-install, grub_efi_x86_64-install, grub_efi_i386-install. Of course this is not needed if only one platform is listed in GRUB_PLATFORMS.
I will look to it in next 14 days...
The problem is that the binaries are simple sh scripts that have no common.sh code that could be easy included based on what platform you want. So one has to detect all the scripts that define the platform stuff and duplicate them...
This should be fixed via --program-transform-name in grub-2.00_beta0.