gallium/targets: rework the empty targets removal

gallium/targets: rework the empty targets removal

Earlier commit added extra tracking and we've attempted to remove the
vdpau/other folder if empty. V2 of said commit dropped the pipe
to /dev/null and the explicit "true" override.

Sadly both of those are needed since there's no guarantee that the
folder will be empty before we [mesa] make install.

Since we're bringing those two back, there's no need to track if we've
installed anything, and simply do "rm -d foo/ &>/dev/null || true"

Tested-by: Andy Furniss <adf.lists@gmail.com>
Reported-by: Andy Furniss <adf.lists@gmail.com>
Fixes: 1cd4fde053 ("gallium/targets: don't leave an empty target directory(ies)")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>