Fix the issue when upstream workflow is used and the addons fork does
not yet have the release branch. In this case create a local branch
which is based on the upstream/<branch> but does not track anything.
Typically with such workflow the local branches will track origin, but
since the origin does not have the branch yet it is not possible to
track it.
Test plan:
- Use upstream workflow
- Have a fork of addons, which does not have blender-v3.6-release
- Run make update
The error message:
```
Updating scripts/addons ...
git fetch origin
git fetch upstream
git checkout -t origin/blender-v3.6-release
fatal: 'origin/blender-v3.6-release' is not a commit and a branch 'blender-v3.6-release' cannot be created from it
make: *** [update] Error 128
```
Pull Request: https://projects.blender.org/blender/blender/pulls/108197
d1254519ad