gstregistry needs to be able to find gst-plugin-scanner which doesn't
exist if tools are disabled, as we do for multilib.

But really, this seems to be papering over a bigger, longer-standing
problem:
* https://bugs.gentoo.org/870361
* https://bugzilla.redhat.com/show_bug.cgi?id=1472160
--- a/tests/check/meson.build
+++ b/tests/check/meson.build
@@ -36,7 +36,7 @@ core_tests = [
   [ 'gst/gstpreset.c' ],
   [ 'gst/gstprotection.c' ],
   [ 'gst/gstquery.c', not gst_registry ],
-  [ 'gst/gstregistry.c', not gst_registry ],
+  [ 'gst/gstregistry.c', not gst_registry or not get_option('tools').enabled() ],
   [ 'gst/gstpromise.c'],
   [ 'gst/gstsegment.c' ],
   [ 'gst/gststream.c' ],