make: factorize code for generating release updates (#12655)

Instead of splitting remove / exclusion of unwanted files in 2-3 places
(`all` rule, `update` rule, and update script in some cases), install
the same files in debug & release builds, and exclude unwanted stuff
when generating the update.

This should finally fix the CI issue with OCR tests (since we don't
remove the `data/dict` & `data/tessdata` directories on release build
anymore).

.github/workflows/build.yml

@@ -197,7 +197,9 @@ jobs:
       # Generate / upload artifact. {{{
 
       - name: Generate artifact
-        run: make update --assume-old=base
+        # Note: ensure the build skeleton is created, so there are no dangling
+        # symlinks (e.g. `data/dict`) to trip 7zip during artifact generation…
+        run: make skeleton update --assume-old=base
 
       - name: Upload artifact
         uses: actions/upload-artifact@v4