`which` utility is not shipped by default for example on recent Arch
Linux and then any steps relying on its presence fails, like for example
following Python3 prereq build check:
$ python3 --version
Python 3.9.1
$ make
/bin/sh: line 1: which: command not found
...
Checking 'python3'... failed.
So make `which` utility host build requirement.
References: PR#3820 FS#3525
Signed-off-by: Petr Štetiar <ynezz@true.cz>
(cherry picked from commit 13069b1a1dcbef0bb9b42db98025fa9203283220)
ceb6869cd9
