meson: Fix map files and load them to hide private symbols

Map files were using wrong syntax (missing final `;` or invalid chars).

Also, the map files were only monitored for rebuilding, but not really used by
ld, so pass the ldflags with version-script so that private symbols are really
hidden.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/395

cogl/cogl-path/libmutter-cogl-path.map

@@ -14,4 +14,4 @@ global:
   cogl2_set_*;
 local:
   *;
-}
+};