Update git clone logic in build.xml

We have encountered lots of test material staging problems (see [build.xml](https://github.com/adoptium/aqa-tests/blob/master/jck/build.xml#L89)). In the build.xml, the logic is complicated as we try to handle lots of different cases.

To make this simple, if git cmd fails, we should remove the pre-staged material and re-clone.

related:
- infrastructure/issues/8508
- backlog/issues/1255
- backlog/issues/1248

Start by reading jck/build.xml around line 89 and trace the existing git clone and pre-staged-material handling. Reproduce or inspect the staging failure path, then verify that a failed git command removes the pre-staged material and retries the clone; confirm the relevant test-material staging flow completes successfully.

Written by the indexing model from the issue text.