Replace strange $TEST_FUNCTIONS variable/expansion thing with
something more like what we use in nbdkit, a simple tests/functions.sh
script that gets sourced into each test script.
Update the common submodule to get:
commit 8137d47d0e654065391151eb275e3b64f230f6f5
Author: Richard W.M. Jones <rjones@redhat.com>
Date: Thu Feb 13 11:13:55 2025 +0000
mlcustomize, mltools: Replace $TEST_FUNCTIONS
TEST_FUNCTIONS is being removed from libguestfs and guestfs-tools (it
was removed from virt-v2v a while back). Make the same adjustment in
the common submodule.
(and some other commits which are not relevant to libguestfs)