Allow -fllvm to be used when compiling unregisterised (#7622)

compiler/main/DynFlags.hs

@@ -3376,7 +3376,7 @@ makeDynFlagsConsistent dflags
       else let dflags' = dflags { hscTarget = HscLlvm }
                warn = "Compiler not unregisterised, so using LLVM rather than compiling via C"
            in loop dflags' warn
- | hscTarget dflags /= HscC &&
+ | hscTarget dflags /= HscC && hscTarget dflags /= HscLlvm &&
    platformUnregisterised (targetPlatform dflags)
     = loop (dflags { hscTarget = HscC })
            "Compiler unregisterised, so compiling via C"