[fix] mandelbrot example temp directory fixed to accommodate Windows

[jjfumero]

Description

Mandelbrot example temp directory fixed to accommodate Windows systems (or any OS).

Problem description

The path was hard-coded to Unix-based systems.

Backend/s tested

Mark the backends affected by this PR.

• [X] OpenCL
• [X] PTX
• [X] SPIRV

OS tested

Mark the OS where this PR is tested.

• [ ] Linux
• [ ] OSx
• [X] Windows

Did you check on FPGAs?

If it is applicable, check your changes on FPGAs.

• [ ] Yes
• [X] No

How to test the new patch?

tornado --threadInfo -m tornado.examples/uk.ac.manchester.tornado.examples.compute.Mandelbrot