This can make it simpler to ensure the same OTP version that builds
the current checkout will match the one that builds the appup base,
since one may change the version locally.
Since the script copies the current workdir into the temporary
directory for the previous build, when we latter try to clean the
directory, `git clean -fdx` refuses to clean the folders of some
dependencies:
```
+ git clean -fdx
Skipping repository _build/default/lib/lc
```
So, if the branch contains a dependency with changed version, it'll
not be picked up by the script, as both versions will be identical and
hence have no `.appup` difference.
Thales Macedo Garitezi