haskell: use GHCJS to build Setup.hs for GHCJS packages

Closes https://github.com/NixOS/nixpkgs/pull/23614.

pkgs/development/haskell-modules/generic-builder.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchurl, ghc, pkgconfig, glibcLocales, coreutils, gnugrep, gnused
-, jailbreak-cabal, hscolour, cpphs
+, jailbreak-cabal, hscolour, cpphs, nodejs
 }: let isCross = (ghc.cross or null) != null; in
 
 { pname
@@ -133,6 +133,7 @@ let
 
   setupCompileFlags = [
     (optionalString (!coreSetup) "-${packageDbFlag}=$packageConfDir")
+    (optionalString isGhcjs "-build-runner")
     (optionalString (isGhcjs || isHaLVM || versionOlder "7.8" ghc.version) "-j$NIX_BUILD_CORES")
     # https://github.com/haskell/cabal/issues/2398
     (optionalString (versionOlder "7.10" ghc.version && !isHaLVM) "-threaded")
@@ -157,7 +158,7 @@ let
 
   ghcEnv = ghc.withPackages (p: haskellBuildInputs);
 
-  setupBuilder = if isCross || isGhcjs then "${nativeGhc}/bin/ghc" else ghcCommand;
+  setupBuilder = if isCross then "${nativeGhc}/bin/ghc" else ghcCommand;
   setupCommand = "./Setup";
   ghcCommand' = if isGhcjs then "ghcjs" else "ghc";
   crossPrefix = if (ghc.cross or null) != null then "${ghc.cross.config}-" else "";
@@ -294,6 +295,14 @@ stdenv.mkDerivation ({
       local pkgId=$( ${gnused}/bin/sed -n -e 's|^id: ||p' $packageConfFile )
       mv $packageConfFile $packageConfDir/$pkgId.conf
     ''}
+    ${optionalString isGhcjs ''
+      for exeDir in "$out/bin/"*.jsexe; do
+        exe="''${exeDir%.jsexe}"
+        printf '%s\n' '#!${nodejs}/bin/node' > "$exe"
+        cat "$exeDir/all.js" >> "$exe"
+        chmod +x "$exe"
+      done
+    ''}
     ${optionalString doCoverage "mkdir -p $out/share && cp -r dist/hpc $out/share"}
     ${optionalString (enableSharedExecutables && isExecutable && !isGhcjs && stdenv.isDarwin && stdenv.lib.versionOlder ghc.version "7.10") ''
       for exe in "$out/bin/"* ; do