dpkg (>= 1.20.3) has better support for its own DPKG_ROOT resulting in
architectures for the root being reported rather than the host system.
Sadly the hookscript from pkg-config is not prepared for this resulting
in our `dpkg --add-architecture` calls failing in the hook after dpkg
has successfully added the architecture internally. The failure
triggered fallback handling in the tests to work with an older version
of dpkg with a different multi-arch implementation.
So instead of doing the fallback, we ignore the failure if it seems like
pkg-config-dpkghook is involved only producing a bunch of warnings
to hint at this problem, but otherwise make the tests work again as it
is a post-invoke script.