Backpack signatures can't be compiled in one shot mode

signature Sig where

data A
data B

foo :: A -> B

[nix-shell:~/ghc-abi]$ ghc Sig.hsig -this-component-id sig -instantiated-with Sig=\<Sig\> -this-unit-id=sig -c
typecheckIfacesForMerging
Declaration for foo:
  Bad interface file: Sig.hi
      Sig.hi: openBinaryFile: does not exist (No such file or directory)
Cannot continue after interface file error