grub-efi-native: fix build on modern distributions without gets()

O irony: the grub2/gnulib nag macro that says "don't use gets, use fgets" breaks the build if you're using a recent (e)glibc release that has gets removed.

Fedora already #if 0's the check in grub, so I stole their patch.

(From OE-Core rev: 261e377b08388a288ee521a3629877b89e18e42b)

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>