doc/hooks/desktop-file-utils: document hook (#341280)

doc/hooks/desktop-file-utils.section.md

@@ -0,0 +1,5 @@
+# desktop-file-utils {#desktop-file-utils}
+
+This setup hook removes the MIME cache (located at `$out/share/applications/mimeinfo.cache`) in the `preFixupPhase`.
+
+This hook is necessary because `mimeinfo.cache` can be created when a package uses `desktop-file-utils`, resulting in collisions if multiple packages are installed that contain this file (as in [#48295](https://github.com/NixOS/nixpkgs/issues/48295)).

doc/hooks/index.md

@@ -12,6 +12,7 @@ bmake.section.md
 breakpoint.section.md
 cernlib.section.md
 cmake.section.md
+desktop-file-utils.section.md
 gdk-pixbuf.section.md
 ghc.section.md
 gnome.section.md