gnu-efi-libs: update to 3.0w and fix build

gnu-efi-libs 3.0v was broken since headers and usr/lib/elf_*_efi.lds was not installed. syslinux does not build with gnu-efi-libs 3.0v as is.

I bumped the version to fix [another regression](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747158) I need fixed for building gummiboot with `-nostdinc`.