Fix compile issues / code smell related to NO_ACTION_MACRO/FUNCTION and LTO_ENABLE

[vomindoraan]

Description

As discussed in #8604, there is currently an issue with how NO_ACTION_MACRO and NO_ACTION_FUNCTION are defined when LTO is enabled using LINK_TIME_OPTIMIZATION_ENABLE/LTO_ENABLE. Namely, common.mk adds these definitions outright and has no way of checking if they already exist somewhere down the pipeline, since the makefile is processed before any headers.

qmk_firmware/tmk_core/common.mk

Lines 158 to 167 in 2f623da

	ifeq ($(strip $(LINK_TIME_OPTIMIZATION_ENABLE)), yes)
	ifeq ($(PLATFORM),CHIBIOS)
	$(info Enabling LTO on ChibiOS-targeting boards is known to have a high likelihood of failure.)
	$(info If unsure, set LINK_TIME_OPTIMIZATION_ENABLE = no.)
	endif
	EXTRAFLAGS += -flto
	TMK_COMMON_DEFS += -DLINK_TIME_OPTIMIZATION_ENABLE
	TMK_COMMON_DEFS += -DNO_ACTION_MACRO
	TMK_COMMON_DEFS += -DNO_ACTION_FUNCTION
	endif

This forces users to check for LTO before defining the macros, which:

1. creates an asymmetry between how NO_ACTION_MACRO/FUNCTION and other NO_ACTION_* flags are used;
2. requires users to know about what is essentially an implementation detail;
3. is a code smell.

At the moment, any keyboard, keymap or userspace that unconditionally defines the above flags will fail to compile with LTO_ENABLE = yes due to the flags already being defined in the makefile.

Background: The defines were originally added to common.mk in #5674, and the LTO check was added to config.h templates in #7211.

Solution

This PR solves the above issues by moving the “if LTO is enabled, legacy macro and function features should be disabled” logic from tmk_core/common.mk into tmk_core/action.h. This keeps the macros available to existing source files that check for NO_ACTION_MACRO/FUNCTION, but it removes the need to check for LTO before defining these macros in keyboard/userspace/keymap files.

Testing

The following keyboards can be used for testing:

claw44
amj96
georgi
scarletbandana
tetris
pearl
uzu42
clueboard/66_hotswap
jc65/v32a
kbdfans/kbd6x
converter/usb_usb/ble
handwired/xealous/rev1
sentraq/s60_x/default

On master, they don't compile if you set LTO_ENABLE = yes. With these changes, they compile correctly.

Types of Changes

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

Issues Fixed or Closed by This PR

• closes NO_ACTION_MACRO and NO_ACTION_FUNCTION when LINK_TIME_OPTIMIZATION_ENABLE is defined. #8604

Checklist

• My code follows the code style of this project.
• 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).

[zvecr]

Thanks!