kdePackages.kservice: handle sycoca disappearing better

This is not a complete fix, the whole thing is still full of races,
but at least this gets it to explode a lot less often.

pkgs/kde/frameworks/kservice/default.nix

···
 mkKdeDerivation {
   pname = "kservice";
 
+  # FIXME(later): upstream
   patches = [
     # follow symlinks when generating sycoca
-    # FIXME(later): upstream
     ./qdiriterator-follow-symlinks.patch
+    # explode less when sycoca is deleted
+    ./handle-sycoca-deletion.patch
   ];
   meta.mainProgram = "kbuildsycoca6";
 }

pkgs/kde/frameworks/kservice/handle-sycoca-deletion.patch

···
+diff --git a/src/sycoca/ksycoca.cpp b/src/sycoca/ksycoca.cpp
+index 981342e6..5940f65f 100644
+--- a/src/sycoca/ksycoca.cpp
++++ b/src/sycoca/ksycoca.cpp
+@@ -218,6 +218,10 @@ KSycoca::KSycoca()
+         connect(d->m_fileWatcher.get(), &KDirWatch::dirty, this, [this]() {
+             d->slotDatabaseChanged();
+         });
++        // NIXPKGS: we sometimes delete sycoca externally
++        connect(d->m_fileWatcher.get(), &KDirWatch::deleted, this, [this]() {
++            d->slotDatabaseChanged();
++        });
+     }
+ }