fix(platformio): 🐛 Use relative paths instead of absolute paths

[ZZ-Cat]

When I initially containerised CFA, I had the hare-brained idea of using absolute paths in CFA's configuration files.
Turns out, this led to obscure permission denial errors whenever I tried to run both PlatformIO commands or CFA's build.py script as a part of the QC and QL workflows.

This resolves the broken QC and QL workflows. Everything should run as expected now.

[ZZ-Cat]

Okay, that's wild. 🤔
I'm getting permission denied for CFA's workspace directory. That's why the CI is failing.

[ZZ-Cat]

Okay, so it seems I am running into permission errors on the /workspaces folder when both the QL and QC scripts try to run build.py or anything else PlatformIO and Python related... 🤔

[ZZ-Cat]

Awesome-sauce! =^/,..,^=
TIL: ALWAYS use relative paths!
Otherwise, I'll get obscure permission issues here, despite CFA building perfectly in my local environment.

That's one headache out of the way.
Now all I need to do is figure out what's going on with the build on compatible targets and why its status is not being reported. I may need to fix that in another branch or so... I don't know yet. But I'm glad I got the main headache that this Pull Request was attempting to fix sorted.

[ZZ-Cat]

I also found out why the build_on_compatible_targets check is infinitely waiting for its status to be reported—it's leftovers from the old way I used to do it, and it has since been amalgamated into my Defect Detector.

So, I'll merge this as-is, because the important checks pass all a-okay. 👌🏼