binman: bintool: bzip2: fix version function on non-Debian-based systems

Upstream bzip2 1.0.x actually is stuck when running bzip2 -V and
redirecting the output. This is fixed in Debian for about a decade
already in
https://git.launchpad.net/ubuntu/+source/bzip2/tree/debian/patches/20-legacy.patch?h=ubuntu/jammy
and in bzip2 1.1.x (no release yet, see
https://gitlab.com/bzip2/bzip2/-/commit/65179284ceddc43e6388bf4ed8c2d85cf16e1b2f


).

Fedora notably does not have such a patch.

Since bzip2 --help actually prints the version number too, let's use it
instead so that binman works fine on (hopefully) all distributions.

Fixes: 45aa2798 ("binman: Add bzip2 bintool")
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>