Add "live-image" and "install-image" target support to build.sh.
"live-image" target builds pre-installed disk images that can be used on
emulators or boot from USB memory sticks to try NetBSD without installation.
Currently amd64, i386, pmax, sparc, sparc64, sun2, sun3, and vax
(which have working emulators and don't require extra tools like preparing
msdosfs or partitioning MD label structures) support this target.
"install-image" target builds an bootable installation disk image that can
be used as an install CD but burned into USB memory sticks etc.
Current only amd64 and i386 (which would support USB boot) have this target.
For more details (and known issue) see following posts on netbsd-bugs@:
http://mail-index.NetBSD.org/netbsd-bugs/2011/08/06/msg023639.html
http://mail-index.NetBSD.org/netbsd-bugs/2011/09/23/msg024207.html
http://mail-index.NetBSD.org/netbsd-bugs/2011/12/07/msg025166.html
http://mail-index.NetBSD.org/netbsd-bugs/2011/12/08/msg025178.html
No particular comments about implementation, and
"go ahead" comments from mrg@, riz@ and christos@.
Closes PR toolchain/45153 and PR misc/45155.
3cf69f27e2