[Core] Re-order user space rules inclusion

[filterpaper]

Description

Re-order inclusion of userspace rules.mk before mcu_selection.mk to support overriding micro controller settings, such as chibios CONVERT_TO converters or MCU selection.

Confirmed binary reproducibility with planck/rev6 and crkbd/rev1.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[drashna]

I'm not sure how I feel about allowing userspace to override the MCU.

It very much feels the opposite of what is supposed to happen (specific to general, keyboard -> keymap -> userspace).

[filterpaper]

keyboard/keymap/rules.mk can overwrite MCU selection but not the copy in userspace. I had the impression that "overwrite" priority is userspace > keymap > keyboard by design.

In its current position, CONVERT_TO= directive also cannot be used in userspace rules.mk.

[spidey3]

This seems to have broken some compiles (I noticed it with when using layouts/community/75_ansi/spidey3).

It seems to have changed ordering of community layout's rules.mk vs. user level rules.mk. In this specific case, layouts/community/75_ansi/spidey3/rules.mk used to be read before users/spidey3/rules.mk; now that is reversed, and it's breaking the ability to turn settings on/off in the community layout, and then react to those settings in the build of the userspace code. It's also inconsistent with the config.h ordering.

An an aside, the docs at https://docs.qmk.fm/#/hardware_keyboard_guidelines?id=rulesmk need to be updated (for this change, and also to explain when community layout rules.mk is loaded).

This could be somewhat fixed by allowing post_rules.mk at the user level, but I suspect that a better way might be to add a pre_rules.mk that would allow user level overrides.