Use sterm instead of cu on ryuglab target

Compared to cu, sterm does not wait 2 seconds after hangup before it exits
(and leaves the port for another user/connection) and can reset the board
via command line switches (no need for --reset-cmd).

Sterm lives at
https://rtime.felk.cvut.cz/gitweb/can-benchmark.git/blob/HEAD:/utils/sterm.c

Additionally, use ssh -tt instead of -t. This causes the sterm to receive
SIGHUP even if ssh does not run on terminal.
gen_cpio: Add support for gzip compression
Added support of Intel AMT
Do not power off during AMT reset
Move "use LWP" to amt block

Novaboot should not fail when LWP is not installed and AMT is not used.
Whitespace and indentation fixes
AMT: cleanups, simplifications
Do not read the script if --on or -off is specified

This allows running novaboot without any script in which case
novaboot does not block in reading from stdin.
Update --amt documentation
Merge branch 'amt'

Conflicts:
	README.md
	novaboot
Make example buildroot use /dev/console for getty

This way, getty appears wherever the user sets console kernel
command line.
Update comments
Do not run amtterm only after reset and get rid of sleep()

This way, amtterm fails is somebody is already connected. Only if amtterm
succeeds, we proceed to reset/poweron.

With recent amttool (at least commit [1]), this works even without sleep
before running amtterm.

[1]: https://www.kraxel.org/cgit/amtterm/log/?h=0ece5135fef56dbd0d94957c334655a57adb7212
AMT: Disconnect SOL before power off

Otherwise power off fails.
Implement run keyword

This allows to run arbitrary commands during file generation phase.
examples: Do not compile buildroot toolchain, just download a pre-built one
pull from wentasah novaboot