Fedora now ships edk2 firmware in its official repos, so adapt
the nvram path list to match. Eventually we can remove the nightly
links as well once some integration kinks have been worked out,
and documentation updated.

Move the macro building into the %build target, which lets us
build up a shell variable and make things a bit more readable

https://bugzilla.redhat.com/show_bug.cgi?id=1335395
(cherry picked from commit e9ef4dfa)