Signed-off-by: Leah Rowe <leah@libreboot.org>

See file:
resources/scripts/build/defconfig/for
It is based on:
resources/scripts/build/payload/u-boot

The u-boot payload script has been deleted, as has the
seabios payload script; the build/boot/roms logic has
been heavily simplified too, by removing the logic for
building of elf files based on defconfig.

SeaBIOS, U-Boot and coreboot all use defconfig-type
infrastructure for their build systems, and they are
fundamentally the *same* in how to compile each codebase,
at least in an lbmk context, regardless of actual (and
very huge) differences in these codebases.

Several hundred sources-lines of code have been eliminated
by this change, drastically simplifying everything; U-Boot
payload compiling also now errors out when a single build
fails, instead of continuing. Also: build/boot/roms no longer
re-compiles a coreboot target that was already compiled,
which is the same behaviour observed for payloads.

(this means you must now manually delete a target, when you
wish to re-build it; the build/boot/roms logic now more or
less just runs cbfstool; blobutil is handled from
build/defconfig/for)

ALSO: Since crossgcc is now handled by build/defconfig/for, not
build/boot/roms, standalone compiling of u-boot is now possible.
This has been tested. You compile it like so:
./build defconfig for u-boot
or specific trees, e.g.
./build defconfig for u-boot default

One other consequence of this patch is that re-building the same
ROM image is now much faster, because the same builds are re-used
unless deleted. This could be useful when testing grub.cfg changes,
for example, if that's all you change. With things like ccache used
(not yet used robustly in lbmk), this could speed things up more,
depending on the codebase.

This patch demonstrates the raw power of lbmk; it is a very
simple and highly efficient build system, and now much more so!

Signed-off-by: Leah Rowe <leah@libreboot.org>

python 3 is default now, in all the distros

specifically calling "python3" often doesn't work anymore

python2 is obsolete

let python2 die

previously, "normal" initmode relied on the vgarom-based
seabios config, which enables option roms, but then lbmk
would insert pci-optionrom-exec 0 for vgarom, and 2 for normal

in libreboot, coreboot roms with "vgarom" in the filename do
pci option rom execution from coreboot, and "normal" roms
do execution from seabios(where seabios is the only payload
provided on normal setups)

this is because payloads like grub can also be used, on vgarom
setups, where coreboot must handle oprom execution

with this change, it's unlikely we'll hit errors again. previously,
some projects used were calling "python" which in context was
python3, but on some setups, the user only has python2 and python3
but no symlink for "python" (which if exists, we assumed linked to
python3)

now it's unambiguous. docs/build/ can probably be updated now, as
a result of this change, to remove the advice about that

this is forked from the "libre" branch in osboot, which is itself a libre,
deblobbed fork of osboot, a blobbed up fork of libreboot

libreboot needed to be purged clean. this is the new libreboot development
repository. the old one has been abandoned