libmusicbrainz5 builds build architecture tools to be run during build.
Since this is fully unsupported by cmake, it circumvents this limitation
using "import executables". Thus, an additional native build pass is
required. It produces a ImportExecutables.cmake to be passed to the
cross build. Refer to INSTALL.txt for details. Long story short, the
attached patch implements what you need. Unfortunately, neon is not
coinstallable, so adding the native neon required for the native build
pass presently makes libmusicbrainz5 cross-bd-uninstallable until
libneon27-gnutls-dev becomes Multi-Arch:same. Please consider applying
the attached patch. If you manage to find a way to perform the native
pass without neon, that'd be awesome.

Helmut