nqp: autopkgtest times out

[Dominique Dumont]

> Since version 2018.03+dfsg-2, the autopkgtests¹ are timing out (~ 3
> hours) while previous runs tested in about 1 minute.
> Could you please investigate how to get rid of the timeout?

Sure. Sorry about the delay. 

The tests should be quite short.

I'm investigating why nqp test blocks in this condition.

I've reproduced this with:
 timeout 5 nqp t/nqp/114-pod-panic.t || echo aborted
1..1
aborted

Note that the test does not block when building nqp... Which is weird..

All the best