The wayland package needs a native wayland-scanner program installed by dev-util/wayland-scanner. It declares this in BDEPEND with MULTILIB_USEDEP which can break cross-compiling to multilib-aware targets. The wayland-scanner ebuild should be able to drop its multilib support and have MULTILIB_USEDEP removed from dev-libs/wayland's BDEPEND, but doing so would require the target libdir to match the BROOT libdir due to bug #762454. When that bug is fixed, there should be no issue making wayland-scanner non-multilib.
commit 82a94e161c7dbb7094a9f808075a92d3f1c22510 Author: Matt Turner <mattst88@gentoo.org> Date: Fri Dec 10 00:44:50 2021 -0500 dev-libs/wayland: Drop multilib requirement on wayland-scanner Signed-off-by: Matt Turner <mattst88@gentoo.org>