Fix `source_archive` ignoring addons

Caused by the changes in the submodules configuration.

Can no longer rely on the `git submodule` command to
show list of external references to be packed.

Needs to be backported to 3.5.1.

Pull Request: https://projects.blender.org/blender/blender/pulls/106502

build_files/utils/make_source_archive.py

@@ -131,9 +131,7 @@ def submodules_to_manifest(
     skip_addon_contrib = version.is_release()
     assert not blender_srcdir.is_absolute()
 
-    for line in git_command("-C", blender_srcdir, "submodule"):
-        submodule = line.split()[1]
-
+    for submodule in ("scripts/addons", "scripts/addons_contrib"):
         # Don't use native slashes as GIT for MS-Windows outputs forward slashes.
         if skip_addon_contrib and submodule == "scripts/addons_contrib":
             continue