enable LTO to bring firmware size down

keyboards/nightly_boards/octopad/rules.mk

@@ -15,6 +15,7 @@ COMMAND_ENABLE = no           # Commands for debug and configuration
 # Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
 SLEEP_LED_ENABLE = no         # Breathing sleep LED during USB suspend
 # if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+LTO_ENABLE = yes              # Link Time Optimization, makes the firmware smaller but some features may not work
 NKRO_ENABLE = no              # USB Nkey Rollover
 BACKLIGHT_ENABLE = no         # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = yes         # Enable keyboard RGB underglow
@@ -23,4 +24,4 @@ AUDIO_ENABLE = yes             # Audio output
 ENCODER_ENABLE = yes          # Enable Rotary Encoders
 
 # Added encoder Action
-SRC +=  encoder_action.c
+SRC +=  encoder_action.c