Bash can be in both /usr/bin/bash or /bin/bash (or elsewhere!) depending on
the distro, so let's be generic using env to figure it out.
This comes from a packaging lintian error we get:
E: mutter-16-tests: wrong-path-for-interpreter /usr/bin/bash != /bin/bash
[usr/share/mutter-16/tests/socket-launch.sh]
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4288>
Launching pipewire and wireplumber is racy, as there is an arbitrary
amount of time between pipewire is launched, and that the socket is
bound.
In order to eliminate this race, bind the pipewire sockets ourselves,
and launch pipewire (and wireplumber) when there is activity on the
socket. This is using the systemd method of doing socket activation,
which consists of passing the number of passed file descriptors via
$LISTEN_FDS, and the pid of the launchee via $LISTEN_PID.
The former is easy, just pass the file descriptors, but the former is
more tricky when using python, as executing code before exec() is poorly
supported and likely to be deprecated. To address this, socket
activation services are wrapped in a socket-launch.sh helper which sets
the $LISTEN_PID to itself before calling exec().
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3973>
