girffi: Add a test for gi_function_info_prep_invoker()

This test case was originally written by Philip Chimento as a reproducer
for #3218. Let’s add it to the test suite to catch regressions in
stack-allocated `GIBaseInfo` handling.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #3218

girepository/tests/meson.build

@@ -6,6 +6,9 @@ if enable_gir
     'cmph-bdz': {
       'dependencies': [cmph_dep],
     },
+    'function-info' : {
+      'depends': [glib_gir],
+    },
     'gthash' : {
       'dependencies': [girepo_gthash_dep],
     },