[LinuxBIOS] Stale payloads

[Myles Watson]

I've been spinning my wheels because of a stale payload.

In the fallback directory, the payload file depends on the
../{../}*/payload.elf file.  If you change that to ../../payload.lzma.elf to
retry, it won't get the new file if payload is newer than payload.lzma.elf.

It seems like there are several possible fixes, but the one I like is
changing buildtarget to remove the payload* files from normal, fallback,
etc.  The problem is that it doesn't look like buildtarget knows about those
directories.

Is there a better way?

Thanks,
Myles