zsh: split documentation into separate outputs

pkgs/shells/zsh/default.nix

@@ -19,6 +19,7 @@ in
 stdenv.mkDerivation {
   pname = "zsh";
   inherit version;
+  outputs = [ "out" "doc" "info" "man" ];
 
   src = fetchurl {
     url = "mirror://sourceforge/zsh/zsh-${version}.tar.xz";
@@ -50,9 +51,8 @@ stdenv.mkDerivation {
   checkFlags = map (T: "TESTNUM=${T}") (lib.stringToCharacters "ABCDEVW");
 
   # XXX: think/discuss about this, also with respect to nixos vs nix-on-X
-  postInstall = lib.optionalString stdenv.isLinux ''
+  postInstall = ''
     make install.info install.html
-    '' + ''
     mkdir -p $out/etc/
     cat > $out/etc/zprofile <<EOF
 if test -e /etc/NIXOS; then
@@ -84,6 +84,8 @@ EOF
     mv $out/etc/zprofile $out/etc/zprofile_zwc_is_used
 
     rm $out/bin/zsh-${version}
+    mkdir -p $out/share/doc/
+    mv $out/share/zsh/htmldoc $out/share/doc/zsh-$version
   '';
   # XXX: patch zsh to take zwc if newer _or equal_