stdenvMulti: Set the configure/install flags in the pre-hook

Flags like $(dev)/include don't always get expanded, e.g. leading to
incorrect pkgconfig files.  So set them in the pre-hook.

pkgs/build-support/multiple-outputs.nix

@@ -6,30 +6,34 @@ with stdenv.lib;
 
 stdenv.mkDerivation (args // {
 
-  configureFlags =
-    optionals (elem "bin" outputs)
-      [ "--bindir=$(bin)/bin" "--mandir=$(bin)/share/man" ]
-    ++ optionals (elem "lib" outputs)
-      [ "--libdir=$(lib)/lib" ]
-    ++ optional (elem "dev" outputs)
-      "--includedir=$(dev)/include"
-    ++ [ (toString args.configureFlags or []) ];
-
-  installFlags =
-    optionals (elem "dev" outputs)
-      [ "pkgconfigdir=$(dev)/lib/pkgconfig" "m4datadir=$(dev)/share/aclocal" "aclocaldir=$(dev)/share/aclocal" ]
-    ++ [ (toString args.installFlags or []) ];
-
   #postPhases = [ "fixupOutputsPhase" ] ++ args.postPhases or [];
 
+  preHook =
+    ''
+      ${optionalString (elem "bin" outputs) ''
+        configureFlags="--bindir=$bin/bin --mandir=$bin/share/man $configureFlags"
+      ''}
+      ${optionalString (elem "lib" outputs) ''
+        configureFlags="--libdir=$lib/lib $configureFlags"
+      ''}
+      ${optionalString (elem "dev" outputs) ''
+        configureFlags="--includedir=$dev/include $configureFlags"
+        installFlags="pkgconfigdir=$dev/lib/pkgconfig m4datadir=$dev/share/aclocal aclocaldir=$dev/share/aclocal $installFlags"
+      ''}
+    '';
+
   preFixup =
     ''
       runHook preFixupOutputs
 
-      if [ -n "$doc" -a -e $out/share/doc ]; then
-        mkdir -p $doc/share/doc
-        mv $out/share/doc/* $doc/share/doc
-        rmdir $out/share/doc
+      if [ -n "$doc" ]; then
+        for i in share/doc share/gtk-doc; do
+          if [ -e $out/$i ]; then
+            mkdir -p $doc/$i
+            mv $out/$i/* $doc/$i/
+            rmdir $out/$i
+          fi
+        done
         rmdir --ignore-fail-on-non-empty $out/share
       fi