When using e.g. -p grub in build/boot/roms, it will
error out. This patch fixes that.

E.g.

./build boot roms t440pmrc_12mb -p grub

Seldom used feature and it was overlooked. Most people
won't use the option that triggered the error.

By making lbmk fully POSIX-compliant, it will be easier to port lbmk to
other systems implementing POSIX such as Alpine Linux and FreeBSD.

Signed-off-by: Ferass 'Vitali64' EL HAFIDI <vitali64pmemail@protonmail.com>

U-Boot runtime configuration is done with a device-tree file, which is
built alongside the executable in the upstream build system, and must be
available to U-Boot at runtime.

This device-tree is normally not linked into the default "u-boot" ELF
file. So far we have been handling it by re-creating a "u-boot.elf" from
the raw binary parts by setting REMAKE_ELF, and using that as the
coreboot payload. Unfortunately, that fails to build for x86 boards,
more specificly the "coreboot" boards upstream.

It's also possible (but discouraged) to set OF_EMBED to embed the
device-tree file into the U-Boot itself, in which case we could use the
"u-boot" file as the payload on the "coreboot" boards. Add support for
using the "u-boot" file as the payload if "u-boot.elf" doesn't exist.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

The roms_helper script skips building crossgcc-i386 if its target
directory exists. Skip it for other architectures as well.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

Add the coreboot-built cross-architecture toolchains to the PATH so that
modules and payloads can use them. When building for a foreign-arch
board, also export CROSS_COMPILE pointing to the appropriate prefix.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

This re-applies commit a69855f7e448 ("Build 32-bit crossgcc for AArch64
as well") which was inexplicably reverted along with unrelated changes.
Mention in a comment that building crossgcc-arm is necessary for
AArch64.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

When overriding which payloads will be built with the -p command line
argument, the roms_helper script builds the Memtest86+ payload before
checking if it should be disabled. Move the build command after the
command line override.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

When overriding which payloads will be built with the -p command line
argument, the roms_helper script doesn't disable the U-Boot payload.
Disable it in this case.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>