Adding a module

If you add a module to GHC, I know you need to extend ghc.cabal.in. But also ghc.mk? Otherwise I get hits If you add a module to GHC, I know you need to extend ghc.cabal.in. But also ghc.mk? Otherwise I get hits /usr/bin/ar: creating rts/dist/build/libHSrts_debug.a Reachable modules from DynFlags out of date Please fix compiler/ghc.mk, or building DLLs on Windows may break (#7780) Extra modules: CoreOpt make[1]: *** [compiler/stage2/dll-split.stamp] Error 1 make[1]: *** Waiting for unfinished jobs.... make: *** [all] Error 2 Is it necessary to have two places to extend? Simon