rWrapper: use runCommand, local build only

This seems more appropriate for a wrapper generator.

pkgs/development/r-modules/wrapper.nix

@@ -1,25 +1,21 @@
-{ stdenv, R, makeWrapper, recommendedPackages, packages }:
+{ runCommand, R, makeWrapper, recommendedPackages, packages }:
 
-stdenv.mkDerivation {
-  name = R.name + "-wrapper";
+runCommand (R.name + "-wrapper") {
+  preferLocalBuild = true;
+  allowSubstitutes = false;
 
-  buildInputs = [makeWrapper R] ++ recommendedPackages ++ packages;
+  buildInputs = [R] ++ recommendedPackages ++ packages;
+
+  nativeBuildInputs = [makeWrapper];
 
   # Make the list of recommended R packages accessible to other packages such as rpy2
-  passthru.recommendedPackages = recommendedPackages;
-
-  unpackPhase = ":";
-
-  installPhase = ''
-    mkdir -p $out/bin
-    cd ${R}/bin
-    for exe in *; do
-      makeWrapper ${R}/bin/$exe $out/bin/$exe \
-        --prefix "R_LIBS_SITE" ":" "$R_LIBS_SITE"
-    done
-  '';
-
-  meta = {
-    platforms = stdenv.lib.platforms.unix;
-  };
+  passthru = { inherit recommendedPackages; };
 }
+''
+mkdir -p $out/bin
+cd ${R}/bin
+for exe in *; do
+  makeWrapper ${R}/bin/$exe $out/bin/$exe \
+    --prefix "R_LIBS_SITE" ":" "$R_LIBS_SITE"
+done
+''