grub-mkrescue --install-modules for multi-platform support

[Andrei Borzenkov]

It was pointed out that this option does not play well. Different
platforms may need different modules that do not exist for other
platforms; if we give it total list, it will error out because some
modules are missing.

address@hidden:~/build/grub> grub2-mkrescue  -o /tmp/foo.iso 
--install-modules="efi_gop" --locales= --themes= --fonts=
grub2-mkrescue: ошибка: не удалось открыть 
«/usr/lib/grub2/i386-pc/efi_gop.mod»: Нет такого файла или каталога.

May be extending it with something like

grub-mkrescue --install-modules=..." --platform=*-efi
--install-modules="..." --platform=i386-pc --install-modules="..."

This would allow also to make other options per-platform.

I understand that workaround is to manually put them where appropriate
but

- it does not interoperate with compression
- it does not resolve dependencies
- it makes tools unaware which modules are