scripts/image: clean up old .img.gz before starting bootloader/releas
util-linux: add host configure opts

... for utl-linux:host
syslinux: build syslinux-host

TODO: ugly. needs some rework
syslinuxrelease: add initial "make image" support

BIG FAT WARNING:
this requires sudo at build-time. may not work with
auto-builds. check your etc/sudoers

BIG FAT WARNING:
this is a work in progress. use only if you know what you are doing.