Fix ghcjs and use ln -s instead of cp

Author: hamishmack

builder/comp-builder.nix

@@ -585,10 +585,10 @@ let
       fi
     '';
 
-    #shellHook = ''
-    #  export PATH="${shellWrappers.drv}/bin:$PATH"
-    #  ${shellHookApplied}
-    #'';
+    shellHook = ''
+      export PATH=$ghc/bin:$PATH
+      ${shellHookApplied}
+    '';
   }
   // haskellLib.optionalHooks {
     # These are the hooks that are not needed by haddock (see commonAttrs for the ones that

builder/ghc-for-component-wrapper.nix

@@ -55,7 +55,7 @@ let
   ''
   # Replace the package database with the one from target package config.
   + ''
-    cp -r $configFiles/${packageCfgDir} $wrappedGhc/${packageCfgDir}
+    ln -s $configFiles/${packageCfgDir} $wrappedGhc/${packageCfgDir}
 
   ''
   # Set the GHC_PLUGINS environment variable according to the plugins for the component.

overlays/default-setup.nix

@@ -9,7 +9,7 @@ let
   nonReinstallablePkgs = ["base" "Cabal"];
   haskellLib = final.haskell-nix.haskellLib;
   defaultSetupSrc =
-    if final.stdenv.hostPlatform.isGhcjs
+    if final.stdenv.targetPlatform.isGhcjs
       then ../builder/Setup.ghcjs.hs
       else ../builder/Setup.hs;
   addDefaultSetup = compiler-nix-name: ghc:

overlays/ghcjs.nix

@@ -3,21 +3,6 @@ final: prev:
   haskell-nix = prev.haskell-nix // ({
     defaultModules = prev.haskell-nix.defaultModules ++ final.lib.optional final.stdenv.hostPlatform.isGhcjs (
       ({ pkgs, buildModules, config, lib, ... }: {
-        # Allow Cabal to be reinstalled so that custom setups will use a Cabal
-        # built with packages.Cabal.patches
-        nonReinstallablePkgs =
-          [ "rts" "ghc-heap" "ghc-prim" "integer-gmp" "integer-simple" "base"
-            "deepseq" "array" "ghc-boot-th" "pretty" "template-haskell"
-            "ghcjs-prim" "ghcjs-th"
-          ]
-          ++ lib.optionals (!config.reinstallableLibGhc) [
-            "ghc-boot"
-            "ghc" "Win32" "array" "binary" "bytestring" "containers"
-            "directory" "filepath" "ghc-boot" "ghc-compact" "ghc-prim"
-            "hpc"
-            "mtl" "parsec" "process" "text" "time" "transformers"
-            "unix" "xhtml" "terminfo"
-          ];
         testWrapper = [((final.writeScriptBin "node-wrapper" ''
           set -euo pipefail
           exe=$1