this is cherry-picked from osbmk. the cherry-pick was
performed by i, leah rowe. this is adapted from shmalebx's
patch there, in osboot

specifically, these patches from osbmk are being imported:

327a39ef058d5385bf8c1a1b09bac8db6a51b016

5139ad4be4df1835ce154f39161eef4f7c31ee1a

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

I was running into a race condition when rebuilding seabios with a high cpu count,
resulting in failure with this error message:

cc1: fatal error: can't open 'out/src/asm-offsets.s' for writing: No such file or directory

Performing the silentoldconfig step before the full make step seems to resolve the failure.

When running ./download all, we have the following error:
    resources/scripts/download/coreboot: Line 52: $1 is not set.

The ./download all command was broken by the following commit:
2bb805e2e07a7d3e1268a09d720ecd13e26af418 (download: Add --help in the
individual download scripts).

Reported-by: madbehaviorus[m] on #libreboot on liberachat
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>