Make Qt work on my machine

Switches eval stuff $STRIP to run_cmd as it'll log errors on failure without verbose mode enabled, and eval was breaking commands that ran just fine otherwise.

Don't download aqt wheel from pip and install it in two separate steps. Ace said there were issues with this for certain Python versions with 0.8, but hopefully enough has been changed that that isn't applicable anymore.

Upgrade aqt from 0.8 to 0.9.2 as there are bugs with 0.8 that stop Qt 5.15.0 from working for some people.

Fall back to Qt 5.14.2 for 64-bit on MSVC 2017 as the package list is broken and that specific combination doesn't work right now.

Change an error message to more accurately reflect the situations it could be printed in.