stdenv/multiple-outputs.sh: small tweaks

- fix in silencing some moveToOutput messages
- allow removing (developer) documentation even without defining outputs
  (note: some paths are auto-removed by default, e.g. gtk-doc and man3)

pkgs/build-support/setup-hooks/multiple-outputs.sh

@@ -106,7 +106,7 @@ moveToOutput() {
             if rmdir "$srcParent"; then
                 echo "Removing empty $srcParent/ and (possibly) its parents"
                 rmdir -p --ignore-fail-on-non-empty "$(readlink -m "$srcParent/..")" \
-                    > /dev/null || true # doesn't ignore failure for some reason
+                    2> /dev/null || true # doesn't ignore failure for some reason
             fi
         done
     done
@@ -114,7 +114,6 @@ moveToOutput() {
 
 # Move documentation to the desired outputs.
 _multioutDocs() {
-    if [ "$outputs" = "out" ]; then return; fi;
     local REMOVE=REMOVE # slightly hacky - we expand ${!outputFoo}
 
     moveToOutput share/info "${!outputInfo}"

pkgs/development/tools/documentation/gtk-doc/default.nix

@@ -10,6 +10,8 @@ stdenv.mkDerivation rec {
     sha256 = "12xmmcnq4138dlbhmqa45wqza8dky4lf856sp80h6xjwl2g7a85l";
   };
 
+  outputDocdev = "out";
+
   # maybe there is a better way to pass the needed dtd and xsl files
   # "-//OASIS//DTD DocBook XML V4.1.2//EN" and "http://docbook.sourceforge.net/release/xsl/current/html/chunk.xsl"
   preConfigure = ''