add 'spkg-check' for Singular

[sagetrac-jakobkroeker]

Add 'build/pkgs/singular/spkg-check' file for Singular.

See also:

#9281

1. it seems that the repackaged singular tarball has no 'Tst' folder?
   This folder contains the Singular regression tests.

Question: could someone repackage Singular 3.1.7p1 and add the 'Tst' folder?

2. Singular has short, long and very long running regression tests.
   Question:
   is there a convention, which tests 'spkg-check' should run, or may 'spkg-check' accept options?

CC: @jpflori @jdemeyer

Component: spkg-check

Keywords: spkg-check Singular

Issue created by migration from https://trac.sagemath.org/ticket/17488

[jdemeyer]

Replying to @sagetrac-jakobkroeker:

2. Singular has short, long and very long running regression tests.
   Question:
   is there a convention, which tests 'spkg-check' should run, or may 'spkg-check' accept options?

There is no convention, but I would try to limit the time to something on the order of 10 minutes.