qmltermwidget: Fix running of {pre,post}Configure

Commit 0055c6a introduced a new preConfigure hook that sets the right
qmake path. Unfortunately the mkDerivation attributes of qmltermwidget
override the whole configurePhase, so this hook isn't run at all.

This fixes the build of qmltermwidget and it now successfully compiles
on my machine.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

pkgs/development/libraries/qmltermwidget/default.nix

@@ -17,7 +17,11 @@ stdenv.mkDerivation rec {
       --replace '$$[QT_INSTALL_QML]' "/lib/qt5/qml/"
   '';
 
-  configurePhase = "qmake PREFIX=$out";
+  configurePhase = ''
+    runHook preConfigure
+    qmake PREFIX=$out
+    runHook postConfigure
+  '';
 
   installPhase=''make INSTALL_ROOT="$out" install'';