[Gnu-efi-discuss] Make: make "make DESTDIR=../foo install" work right

[Richard H. <hug...@gm...>]

This makes the normal DESTDIR= variable work on the command line, and
makes relative paths always relative to the top-level directory.

Signed-off-by: Peter Jones <pj...@re...>

We've been using this patch in Fedora since 2019. Original patch is by
Peter Jones, sent with permission.

Richard