Cant build SITL on HW - possible result in moving of folder into Tools/scripts - .waf issue, then tmp issue

## Bug report

**Issue details**
I am unable to run the SITL on HW as described in documentation. Appears to be an issue with the move of SITL on HW into Tools/scripts. Code within the sitl_on_hw.py file calls .waf from one level up, which is now 3 levels up.

After amending this in the code fork, I am now faced with an issue with unable to find the .tmp folder.
Rather than try hack away for myself, I thought id better raise it to be properly amended so that any future person looking to build SITL on HW may not come across the same issues.

Start with Tools/scripts/sitl_on_hw.py and reproduce the SITL-on-HW build using the documented procedure. Trace the script's paths to .waf and the .tmp folder after the move, then verify that the documented build completes without manual path changes and can locate the required temporary files.

Written by the indexing model from the issue text.