Fix compile issues related to NO_ACTION_MACRO/FUNCTION and LTO_ENABLE (#8663)

* Define NO_ACTION_MACRO/FUNCTION in header instead of makefile when LTO is enabled

Currently, boards and keymaps that define NO_ACTION_MACRO/FUNCTION unconditionally
will not compile with LTO_ENABLE (#8604). This fixes the issue by moving the
definitions from common.mk to action.h, which enables us to check for previous
definitions of those macros (this cannot be done in a makefile).

* Remove LTO checks in templates

Since now NO_ACTION_MACRO/FUNCTION are defined as needed in action.h (which is
included by quantum.h), checking for LTO in keyboard and user code is no
longer required.

* Update LTO_ENABLE docs

2 files changed, 10 insertions, 2 deletions

diff --git a/tmk_core/common.mk b/tmk_core/common.mk
index 4d4272d26..3d0b83a01 100644
--- a/tmk_core/common.mk
+++ b/tmk_core/common.mk
@@ -162,8 +162,6 @@ ifeq ($(strip $(LINK_TIME_OPTIMIZATION_ENABLE)), yes)
     endif
     EXTRAFLAGS += -flto
     TMK_COMMON_DEFS += -DLINK_TIME_OPTIMIZATION_ENABLE
-    TMK_COMMON_DEFS += -DNO_ACTION_MACRO
-    TMK_COMMON_DEFS += -DNO_ACTION_FUNCTION
 endif
 
 # Search Path
diff --git a/tmk_core/common/action.h b/tmk_core/common/action.h
index dd22023f9..c82c9c81b 100644
--- a/tmk_core/common/action.h
+++ b/tmk_core/common/action.h
@@ -28,6 +28,16 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 extern "C" {
 #endif
 
+/* Disable macro and function features when LTO is enabled, since they break */
+#ifdef LINK_TIME_OPTIMIZATION_ENABLE
+#    ifndef NO_ACTION_MACRO
+#        define NO_ACTION_MACRO
+#    endif
+#    ifndef NO_ACTION_FUNCTION
+#        define NO_ACTION_FUNCTION
+#    endif
+#endif
+
 /* tapping count and state */
 typedef struct {
     bool    interrupted : 1;