build-sys: initialize efi specific stuff
build-sys: initialize efi specific stuff

 - probe for gnu-efi headers
 - probe for gnu-efi libs and gnu-efi linker scripts
 - sets $CC for .efi compilation

Signed-off-by: Karel Zak <b517c2d99ca3f904174ad92ae4446c78e81c3cf1@redhat.com>

miguelinux/gummiboot2systemd-boot,FrozenCow/gummiboot,miguelinux/gummiboot2systemd-boot,todorez/tummiboot,todorez/tummiboot,freedesktop-unofficial-mirror/gummiboot,liliang365/my_gummiboot,aaronp24/gummiboot,todorez/gummiboot-multiboot2,trilean/gummiboot,todorez/gummiboot-multiboot2,aaronp24/gummiboot,trilean/gummiboot,freedesktop-unofficial-mirror/gummiboot,FrozenCow/gummiboot,liliang365/my_gummiboot