validate: generate valgrind suppression traces

Makes fixing easier as then we can just re-use the generated trace.

Reviewed-by: Thibault Saunier <tsaunier@gnome.org>
Differential Revision: https://phabricator.freedesktop.org/D953

validate/launcher/baseclasses.py

@@ -335,6 +335,7 @@ class Test(Loggable):
             ('num-callers', '20'),
             ('log-file', '"' + vglogsfile + '"'),
             ('error-exitcode', str(VALGRIND_ERROR_CODE)),
+            ('gen-suppressions', 'all'),
         ]
 
         for supp in self.get_valgrind_suppressions():