qt48: I give up, switching off parallel building

I was unable to find a reliable fix for the problems.
I seem to get either this http://hydra.nixos.org/build/5326327/nixlog/1/tail-reload
or that http://hydra.nixos.org/build/5297462/nixlog/1/tail-reload .
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#	modified:   pkgs/development/libraries/qt-4.x/4.8/default.nix
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# Untracked files:
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#	core
#	dev.diff
#	pkgs/applications/networking/browsers/firefox/cairo-test.patch
#	pkgs/applications/video/flowblade/
#	pkgs/desktops/gnome-3/core/dconf/
#	pkgs/desktops/gnome-3/core/eog/
#	pkgs/desktops/gnome-3/core/libsecret/
#	pkgs/development/libraries/ncurses/builder.sh
#	pkgs/servers/x11/xorg/download-cache/
#	pkgs/servers/x11/xorg/still-missing.txt

pkgs/development/libraries/qt-4.x/4.8/default.nix

@@ -90,12 +90,6 @@ stdenv.mkDerivation rec {
       ${if developerBuild then "-developer-build" else ""}
     '';
 
-  # fix underspecified dependency in a generated makefile
-  postConfigure = stdenv.lib.optional developerBuild ''
-    sed "1iqtgradientview.h: .uic/release-shared/ui_qtgradientview.h" \
-      -i tools/designer/src/lib/Makefile
-  '';
-
   propagatedBuildInputs =
     [ libXrender libXrandr libXinerama libXcursor libXext libXfixes
       libXv libXi libSM
@@ -113,7 +107,9 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ perl pkgconfig which ];
 
-  enableParallelBuilding = true;
+  # occasional build problems if one has too many cores (like on Hydra)
+  # @vcunat has been unable to find a *reliable* fix
+  enableParallelBuilding = false;
 
   crossAttrs = let
     isMingw = stdenv.cross.config == "i686-pc-mingw32" ||