ghc-stage1: panic! (the 'impossible' happened) creating cross compiler for PPC

We have a product based on a Freescale MPC8544E.

I have previously built powerpc-unknown-linux-gnuspe-ghc-7.8.3 and that produces viable code though annoyingly rather large binaries but this is covered elsewhere.

I looked at both 7.8.4 and 7.10 a while ago but they proved to be non-starters for reasons I no longer remember.

Now for reasons tooling reasons (Stack and friends) it would be nice to use 8.0.2

My procedure is as follows

In the (ghc-7.83 or) ghc-8.0.2 source directory

base=powerpc-unknown-linux-gnuspe; ./configure --prefix=/tmp/prefix --target=$base --with-gcc=$base-gcc --with-ld=$base-ld --with-nm=$base-nm --with-ar=$base-ar --with-ranlib=$base-ranlib --enable-unregisterised

I edit mk/build.mk to make flavour "quick-cross"

I edit ghc.mk and comment out anything with haskeline or terminfo

The bottom of settings says ("Unregisterised", "YES"), ("LLVM llc command", "/usr/bin/llc-3.7"), ("LLVM opt command", "/usr/bin/opt-3.7")

But the make itself (on Ubuntu 16 amd64) fails.

"inplace/bin/ghc-stage1" -hisuf hi -osuf  o -hcsuf hc -static  -O0 -H64m -Wall      -this-unit-id ghc-prim-0.5.0.0 -hide-all-packages -i -ilibraries/ghc-prim/. -ilibraries/ghc-prim/dist-install/build -ilibraries/ghc-prim/dist-install/build/autogen -Ilibraries/ghc-prim/dist-install/build -Ilibraries/ghc-prim/dist-install/build/autogen -Ilibraries/ghc-prim/.    -optP-include -optPlibraries/ghc-prim/dist-install/build/autogen/cabal_macros.h -package-id rts -this-unit-id ghc-prim -XHaskell2010 -O -fllvm  -no-user-package-db -rtsopts -Wno-trustworthy-safe -Wno-deprecated-flags     -Wnoncanonical-monad-instances  -odir libraries/ghc-prim/dist-install/build -hidir libraries/ghc-prim/dist-install/build -stubdir libraries/ghc-prim/dist-install/build    -c libraries/ghc-prim/./GHC/Types.hs -o libraries/ghc-prim/dist-install/build/GHC/Types.o
ghc-stage1: panic! (the 'impossible' happened)
  (GHC version 8.0.2 for powerpc-unknown-linux):
        LlvmCodeGen.Ppr: Cross compiling without valid target info.