Add qemu-user-static for cross-arch build emulation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: shanemcd

mybox/Containerfile

@@ -91,6 +91,8 @@ RUN <<EORUN
         qemu-kvm \
         qemu-system-$(uname -m) \
         qemu-ui-gtk \
+        qemu-user-binfmt \
+        qemu-user-static \
         quickemu \
         virt-install \
         virt-manager \