Spectacle's Desktop file assumes that `qdbus` is in $PATH. However this is not
guaranteed; the actual name of the command is `qdbus-qt<version>` in the distro's Qt
binaries dir. Distros typically create symlinks to these commands in `/usr/bin`, but
not all go a step further and create a second cimpatibility symlink at `/usr/bin/qdbus`
Therefore, we should find the command in the Qt binaries dir itself rarher than relying
on these compatibility symlinks.
BUG: 413007
FIXED-IN: 20.04.0