girepository: Exclude private symbols from the ABI

This removes the gthash utility functions from the ABI, so link those
into their automated test statically.

Signed-off-by: Simon McVittie <smcv@collabora.com>

girepository/tests/meson.build

@@ -6,7 +6,9 @@ if enable_gir
     'cmph-bdz': {
       'dependencies': [cmph_dep],
     },
-    'gthash' : {},
+    'gthash' : {
+      'dependencies': [girepo_gthash_dep],
+    },
     'repository' : {
       'depends': [glib_gir, gobject_gir],
     },