kexi: patch error due to Qt 5.13

(cherry picked from commit 550d67c)

pkgs/applications/office/kexi/default.nix

@@ -1,5 +1,5 @@
 {
-  mkDerivation, lib, fetchurl, extra-cmake-modules, kdoctools,
+  mkDerivation, lib, fetchurl, fetchpatch, extra-cmake-modules, kdoctools,
   boost, qttools, qtwebkit,
   breeze-icons, karchive, kcodecs, kcompletion, kconfig, kconfigwidgets, kcoreaddons,
   kcrash, kguiaddons, ki18n, kiconthemes, kitemviews, kio, ktexteditor, ktextwidgets,
@@ -28,6 +28,17 @@ mkDerivation rec {
 
   propagatedUserEnvPkgs = [ kproperty ];
 
+  patches = [
+    # Changes in Qt 5.13 mean that QDate isn't exported from certain places,
+    # which the build was relying on. This patch explicitly imports QDate where
+    # needed.
+    # Should be unnecessary with kexi >= 3.3
+    (fetchpatch {
+      url = "https://cgit.kde.org/kexi.git/patch/src/plugins/forms/widgets/kexidbdatepicker.cpp?id=511d99b7745a6ce87a208bdbf69e631f1f136d53";
+      sha256 = "0m5cwq2v46gb1b12p7acck6dadvn7sw4xf8lkqikj9hvzq3r1dnj";
+    })
+  ];
+
   meta = with lib; {
     description = "A open source visual database applications creator, a long-awaited competitor for programs like MS Access or Filemaker";
     longDescription = ''