feat: Enable LTO

This uses "fat" binaries, so normal builds won't break, but also includes the LTO data for builds that wish to use it

Makefile

@@ -25,6 +25,7 @@ INCLUDES	:=	include
 #---------------------------------------------------------------------------------
 CFLAGS	:=	-g -Wall -Werror -save-temps \
 			-ffunction-sections -fdata-sections \
+			-flto -ffat-lto-objects \
 			$(MACHDEP) \
 			$(BUILD_CFLAGS)