Makefile fixes

[plusky]

No description provided.

[jsmeix]

@gozora
it would help me a lot for building ebiso
in a clean way in the openSUSE build service
if this enhancement was included in an ebiso release.

[gozora]

Really have no problem with this merge, I'm bit worried about building ebiso on 32-bit architectures.
Not sure whether there aren't some pitfalls.

[jsmeix]

At least for now I do not build ebiso on 32-bit architectures.
I have in ebiso.spec

# ebiso is only used by rear to make UEFI bootable ISO images
# on SLE12 systems so that no other architecture except x86_64 is needed
# (if also needed for 32-bit it could be "ExclusiveArch: %ix86 x86_64"):
ExclusiveArch:  x86_64

But it is nice to have when ebiso can be built
also on non-x6_64 architectures without the need
for changes in its code.

[gozora]

@jsmeix currently I can't recall nothing that could avoid creating EFI bootable ISOs on 32-bit architectures, but it was never tested and I wold not like to put people into trouble especially in such stressful situations like bare metal restores.
Anyhow I'll put 32-bit testing on my todo list ...