Umount detaches the loop device automatically, but let's make it explicit to be sure. Additionally losetup gives: losetup: /dev/loop0: detach failed: No such device or address This is kind of expected, let's silent the error message.
Building images works fine. Enable it by adding use_overlayfs="true" to manjaro-tools.conf.
The miso_overlayfs hook doesn't work, to test change the miso hook to miso_overlayfs.
