Generalise CTPC logic from common_features (#18803)

builddefs/build_keyboard.mk

@@ -368,6 +368,10 @@ endif
 # Disable features that a keyboard doesn't support
 -include $(BUILDDEFS_PATH)/disable_features.mk
 
+ifneq ("$(CONVERTER)","")
+    -include $(CONVERTER)/post_converter.mk
+endif
+
 # Pull in post_rules.mk files from all our subfolders
 ifneq ("$(wildcard $(KEYBOARD_PATH_1)/post_rules.mk)","")
     include $(KEYBOARD_PATH_1)/post_rules.mk

builddefs/common_features.mk

@@ -539,11 +539,7 @@ endif
 VALID_BACKLIGHT_TYPES := pwm timer software custom
 
 BACKLIGHT_ENABLE ?= no
-ifeq ($(strip $(CONVERT_TO_PROTON_C)), yes)
+BACKLIGHT_DRIVER ?= pwm
-    BACKLIGHT_DRIVER ?= software
-else
-    BACKLIGHT_DRIVER ?= pwm
-endif
 ifeq ($(strip $(BACKLIGHT_ENABLE)), yes)
     ifeq ($(filter $(BACKLIGHT_DRIVER),$(VALID_BACKLIGHT_TYPES)),)
         $(call CATASTROPHIC_ERROR,Invalid BACKLIGHT_DRIVER,BACKLIGHT_DRIVER="$(BACKLIGHT_DRIVER)" is not a valid backlight type)

platforms/chibios/converters/promicro_to_proton_c/post_converter.mk

@@ -0,0 +1 @@
+BACKLIGHT_DRIVER ?= software