add only the first OS X system we find
add only the first OS X system we find

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