Disable pyenv cache for linux because maturin is bugged as hell

[evandrocoan]

1. df319c7 - is:review should include relearning cards
2. c50fa2c - invalidate cache

https://github.com/ankitects/anki/runs/852260154#step:25:768

FTL_TEMPLATE_DIRS="../qt/ftl" FTL_LOCALE_DIRS="../qt/ftl/repo/desktop" 
CARGO_TARGET_DIR="/home/runner/work/anki/anki/target" \
	maturin develop 
🔗 Found pyo3 bindings
🐍 Found CPython 3.7m at python
💥 maturin failed
  Caused by: Expected `python` to be a python interpreter inside a virtualenv ಠ_ಠ

[dae]

Busting the cache again seems to have fixed it for now - maybe GitHub are just moving files around?

[evandrocoan]

It could be. Although looking at the cache restoring it does not show the cache was not fully restored (as it may happen).

But, without closely debugging why maturing is thinking he is not inside a virtual env, is hard to tell.

I know that was quite cumbersome to have this maturing detection working on Windows:

1. Expected python to be a python interpreter inside a virtualenv PyO3/maturin#283 - Expected python to be a python interpreter inside a virtualenv

They do not seem to do a robust detection and keep relying on fragile strategy.

[dae]

Let's keep this open for a while and see if the problem pops up again - I'd rather not lose the cache if we can avoid it.