Docker build environment

[NiKiZe]

All I'm talking about is how to modify the make cmd line
See http://ipxe.org/appnote/buildtargets for different buildtargets - for example they are need for supporting usb nics with ecm--ncm--axge as one example.
make everything just in most cases just slow without benefit - since you most likely only want one or 2 binaries in the same build

yes EMBED= for scripts

DEBUG= as seen at http://ipxe.org/download#debug_builds

another tip, use make -j4 or even make -j8 for parallel builds which considerably speeds up things.