TEST: Disable shared tabling tests conditionally.

This test requires threads and library(time).

src/Tests/tabling/test_shared_units.pl

@@ -3,9 +3,10 @@
     Author:        Jan Wielemaker
     E-mail:        [email protected]
     WWW:           http://www.swi-prolog.org
-    Copyright (c)  2019, University of Amsterdam
-                         VU University Amsterdam
-		         CWI, Amsterdam
+    Copyright (c)  2019-2023, University of Amsterdam
+                              VU University Amsterdam
+		              CWI, Amsterdam
+                              SWI-Prolog Solutions b.v.
     All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
@@ -37,6 +38,10 @@
 :- module(test_shared_units,
           [ test_shared_units/0
           ]).
+
+:- if((exists_source(library(time)),
+       current_prolog_flag(threads,true))).
+
 :- use_module(library(plunit)).
 :- use_module(library(debug)).
 :- use_module(library(time)).
@@ -71,3 +76,9 @@
     thread_join(Id).
 
 :- end_tests(shared_reeval).
+
+:- else.                                % no library(time) or no threads.
+
+test_shared_units.
+
+:- endif.