[KConfig] Improve comments in pio.ini : Does not compile if no shield set in platformio.ini

[luizvilla]

Describe the bug
At this moment it is possible to choose between the ownverter and the twist boards for compiling the shields. However, there is no "no_shield" support in the code.

To Reproduce
Steps to reproduce the behavior:

1. Go to platformio.ini
2. Replace board_shield_version by anything but ownverter or twist
3. Build
4. See error

Expected behavior
If there is no shield, the user should be able de deactivate the "shield" api

[jalinei]

Reproduced on my machine today.

There is no need for a no_shield argument. At the moment commenting out these parameters from platformio.ini does correctly suppress shield settings in the CMakeLists.txt
The culprit is to be found in KConfig..

[luizvilla]

I am not sure I agree with this. How will the user only work with the spin then ?

We have "supported shields" written somewhere. We should at least clearly state that if the user does not want a shield, the parameter should be blank.

[jalinei]

I am not sure I agree with this. How will the user only work with the spin then ?

Just by commenting the shield and shield version lines, I agree though, comments should be improved,

I was just pointing out that the option does already exist, and the bug root cause is not PIO but somewhere in KConfig..