Append to CMAKE_MODULE_PATH instead of fully overwriting it. If we fully overwrite the path, then other directories which may have been provided via CMAKE_PREFIX_PATH don't get searched. This causes breakages on the Windows CI as CMake, QCA and ECM are all installed in different prefixes. The existing code will capture items 1 and 3 here, meaning QCA won't be found. This problem doesn't show up on FreeBSD and Linux as CMake and QCA are in the same install prefix