build-sys: fix gcc v5 hickup
build-sys: fix gcc v5 hickup

miguelinux/gummiboot2systemd-boot,freedesktop-unofficial-mirror/gummiboot,trilean/gummiboot,aaronp24/gummiboot,trilean/gummiboot,aaronp24/gummiboot,miguelinux/gummiboot2systemd-boot,freedesktop-unofficial-mirror/gummiboot