Fix crash due to double-free in libxmlb
This MR ports the bugfix for libxmlb to allow the store to work without crashing.
Libxmlb is currently available in the SDK, so this patch must not only to compile it, but also to priorize the libraries in the snap over the ones in the CONTENTS snap.
Bug: https://bugs.launchpad.net/snap-store-desktop/+bug/1988440
Edited by Sergio Costas