directly support heads-setup using x230-flash

[merge]

The Heads project includes a "x230-flash" target to support "bootstrapping" on the X230. That's at least some source for confusion for users, and we're not supposed to add to that. Currently:

• The heads "installing" wiki even links to our "external_install_bottom.sh" script, because that can directly be used when flashing "x230-flash" (just another 4M coreboot build) to the top chip.
• We include a "x230_heads.sh" script, that, in turn, is only usable from a running Linux, and for flashing a full Heads ("x230" target) build.

We can think about improving the situation by

• adding a Heads "x230-flash" image directly to our X230 release package, as a 3rd option
• documenting that as part of our guide as "Install Heads / no running Linux required on disk", and:
• remove our "x230_heads.sh" script, because Heads is supposed to be flashed from whithin itself, only.

What would be (legally) required to add? Link to the Heads sources? Document how to build a full Heads image from source.

Or should we not add an image, but only document (and maybe distribute images via an independent "unofficial" project?)?

[savchenko]

> What would be (legally) required to add?

Heads is licensed under GPL v2.0 (https://github.com/osresearch/heads/blob/master/COPYING). Some relevant excerpts:

p2(a):

...modified files to carry prominent notices stating that you changed the files and the date of any change...

p2(b)

...no charge to all third parties..

p2(b)

If the modified program normally reads commands interactively... print or display an announcement including an appropriate copyright notice...

p3(a)

Accompany it with the complete corresponding machine-readable source code.

TL;DR If Skulls is derived from GPL project, it shall be distributed in GPL-compliant way.