Migrate build target markers to keyboard.json - Misc (#23609)

keyboards/matrix/abelx/keyboard.json

@@ -34,6 +34,8 @@
     "extrakey": true,
     "rgblight": true
   },
+  "processor": "STM32F411",
+  "bootloader": "custom",
   "layouts": {
     "LAYOUT_tkl_ansi": {
       "layout": [

keyboards/matrix/abelx/rules.mk

@@ -1,33 +1,7 @@
-#
-# - the next two should match the directories in
-#   <chibios>/os/hal/ports/$(MCU_FAMILY)/$(MCU_SERIES)
-MCU_FAMILY = STM32
-MCU_SERIES = STM32F4xx
-
-# Linker script to use
-# - it should exist either in <chibios>/os/common/ports/ARMCMx/compilers/GCC/ld/
-#   or <this_dir>/ld/
+# custom bootloader
 MCU_LDSCRIPT = abelx_boot
-
-# Startup code to use
-#  - it should exist in <chibios>/os/common/startup/ARMCMx/compilers/GCC/mk/
-MCU_STARTUP = stm32f4xx
-
-# Board: it should exist either in <chibios>/os/hal/boards/
-#  or <this_dir>/boards
 BOARD = abelx_bd
 
-# Cortex version
-MCU  = cortex-m4
-
-# ARM version, CORTEX-M0/M1 are 6, CORTEX-M3/M4/M7 are 7
-ARMV = 7
-
-USE_FPU = yes
-
-# Bootloader selection
-BOOTLOADER = custom
-
 CUSTOM_MATRIX = lite
 # project specific files
 SRC += matrix.c tca6424.c aw9523b.c