x86 release builds are slow

[Andrew Doran <ad%netbsd.org@localhost>]

Hi,

For an i386 release build we now build 11 kernels, which takes a long time.
To help verification of changes it would be better if release builds didn't
take so long.

For i386 and amd64, we could change the process so that the GENERIC kernel
is used for installs, and the root file system objcopy'd into a seperate ELF
binary that is loaded by the boot loader. We could modify the in-kernel ELF
linker to set the root file system image up. Any comments on that?

For xen that might not be possible because GRUB is used. I don't know. If it
can't be done, what are the major reasons for having seperate DOM0 and DOMU
kernels?

Thanks.
Andrew