Unbreak aarch64-linux-musl-cross

When compiling linux -> linux, but different arch, we _are_ building a cross compiler. Only for same arch we can pretend it's a stage2 compiler.

Author: angerman

compiler/ghc/default.nix

@@ -754,7 +754,7 @@ stdenv.mkDerivation (rec {
       --replace 'dynamic-library-dirs:' 'dynamic-library-dirs: ${libcxx}/lib ${libcxxabi}/lib'
     find . -name 'system*.conf*'
     cat mk/system-cxx-std-lib-1.0.conf
-  '' + lib.optionalString (installStage1 && stdenv.targetPlatform.isMusl) ''
+  '' + lib.optionalString (installStage1 && !haskell-nix.haskellLib.isCrossTarget && stdenv.targetPlatform.isMusl) ''
     substituteInPlace hadrian/cfg/system.config \
       --replace 'cross-compiling       = YES' \
                 'cross-compiling       = NO'