Size fix for Hadron, take 2 (#4009)

* Add Link Time Optimization to reduce firmware size

* Disable Mousekeys on Hadron to save room

keyboards/hadron/keymaps/default/rules.mk

@@ -5,7 +5,7 @@
 #   the appropriate keymap folder that will get included automatically
 #
 BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration(+1000)
-MOUSEKEY_ENABLE = yes      # Mouse keys(+4700)
+MOUSEKEY_ENABLE = no      # Mouse keys(+4700)
 EXTRAKEY_ENABLE = no       # Audio control and System control(+450)
 CONSOLE_ENABLE = no         # Console for debug(+400)
 COMMAND_ENABLE = no        # Commands for debug and configuration

keyboards/hadron/rules.mk

@@ -71,3 +71,5 @@ SRC = i2c.c \
 	  ssd1306.c
 
 DEFAULT_FOLDER = hadron/ver2
+
+EXTRAFLAGS += -flto