[Keyboard] Fix compilation issues for mechlovin hex4b (#15885)

data/mappings/keyboard_aliases.json

@@ -344,6 +344,9 @@
     'mechlovin/hannah65/mechlovin9': {
           target: 'mechlovin/mechlovin9/rev1'
     },
+    'mechlovin/hex4b': {
+          target: 'mechlovin/hex4b/rev1'
+    },
     'melgeek/z70ultra': {
           target: 'melgeek/z70ultra/rev1'
     },

keyboards/mechlovin/hex4b/rules.mk

@@ -1,21 +1 @@
-# MCU name
-MCU = atmega32a
-
-# Bootloader selection
-BOOTLOADER = usbasploader
-
-# Processor frequency
-F_CPU = 16000000
-
-# Build Options
-#   change yes to no to disable
-#
-BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
-MOUSEKEY_ENABLE = yes       # Mouse keys
-EXTRAKEY_ENABLE = yes       # Audio control and System control
-CONSOLE_ENABLE = no         # Console for debug
-COMMAND_ENABLE = no         # Commands for debug and configuration
-NKRO_ENABLE = no            # Enable N-Key Rollover
-BACKLIGHT_ENABLE = yes      # Enable keyboard backlight functionality
-RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
-AUDIO_ENABLE = no           # Audio output
+DEFAULT_FOLDER = mechlovin/hex4b/rev1