bitlbee: fix build

pkgs/applications/networking/instant-messengers/bitlbee/default.nix

@@ -15,9 +15,6 @@ stdenv.mkDerivation rec {
   buildInputs = [ gnutls glib libotr python ]
     ++ optional enableLibPurple pidgin;
 
-  preConfigure = optionalString enableLibPurple
-    "export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:${pidgin}/lib/pkgconfig";
-
   configureFlags = [
     "--gcov=1"
     "--otr=1"
@@ -26,12 +23,12 @@ stdenv.mkDerivation rec {
   ]
   ++ optional enableLibPurple "--purple=1";
 
-  buildPhase = optionalString (!enableLibPurple) ''
-    make install-dev
-  '';
+  installTargets = [ "install" "install-dev" ];
 
   doCheck = !enableLibPurple; # Checks fail with libpurple for some reason
 
+  enableParallelBuilding = true;
+
   meta = {
     description = "IRC instant messaging gateway";