Build-Depend on infernal
Build-Depend on infernal to block the package being built on architectures where it's not available.
Discussion
There is a bug here because trnascan-se could build uninstallable binaries on architectures that don't have infernal.
Interestingly, Debian itself is not affected by this bug because binaries are not built for other architectures for non-free packages unless the package has opted in to autobuilding.
It did affect Ubuntu though which is where this fix comes from.
cc/ @tille