fcitx: drop patches, use extra-cmake-modules directly

Fixes #17252. (Really, this time.)

Now that extra-cmake-modules does not depend on Qt 5, it is possible to
depend on it directly.

pkgs/tools/inputmethods/fcitx/unwrapped.nix

@@ -1,7 +1,7 @@
 { stdenv, fetchurl, pkgconfig, cmake, intltool, gettext
 , libxml2, enchant, isocodes, icu, libpthreadstubs
 , pango, cairo, libxkbfile, libXau, libXdmcp, libxkbcommon
-, dbus, gtk2, gtk3, qt4, kde5
+, dbus, gtk2, gtk3, qt4, extra-cmake-modules
 }:
 
 stdenv.mkDerivation rec {
@@ -13,22 +13,16 @@ stdenv.mkDerivation rec {
     sha256 = "0xvcmm4yi7kagf55d0yl3ql5ssbkm9410fwbz3kd988pchichdsk";
   };
 
-  postUnpack = ''
-    ln -s ${kde5.extra-cmake-modules}/share/ECM/modules/ECMFindModuleHelpers.cmake \
-      $sourceRoot/cmake/
-  '';
-
-  patches = [ ./fcitx-ecm.patch ];
-
   postPatch = ''
     substituteInPlace src/frontend/qt/CMakeLists.txt \
       --replace $\{QT_PLUGINS_DIR} $out/lib/qt4/plugins
   '';
 
+  nativeBuildInputs = [ cmake extra-cmake-modules intltool pkgconfig ];
+
   buildInputs = [
-    cmake enchant gettext isocodes pkgconfig intltool icu
-    libpthreadstubs libXau libXdmcp libxkbfile libxkbcommon libxml2
-    dbus cairo gtk2 gtk3 pango qt4
+    enchant gettext isocodes icu libpthreadstubs libXau libXdmcp libxkbfile
+    libxkbcommon libxml2 dbus cairo gtk2 gtk3 pango qt4
   ];
 
   cmakeFlags = ''