Add java runtime requirement

Signed-off-by: Michael Barton <mail@michaelbarton.me.uk>
Run output in a temporary directory

Signed-off-by: Michael Barton <mail@michaelbarton.me.uk>
Only requirements appear to be /usr/bin/file and a java runtime

Signed-off-by: Michael Barton <mail@michaelbarton.me.uk>
Run assembly in a tmp directory, and prefix is not a directory

Signed-off-by: Michael Barton <mail@michaelbarton.me.uk>
Make assembly prefix explicit

Signed-off-by: Michael Barton <mail@michaelbarton.me.uk>