Add build system for fusee

exosphere/Makefile

@@ -1,7 +1,7 @@
 rwildcard = $(foreach d, $(wildcard $1*), $(filter $(subst *, %, $2), $d) $(call rwildcard, $d/, $2))
 
 ifeq ($(strip $(DEVKITPRO)),)
-$(error "Please set DEVKITARM in your environment. export DEVKITARM=<path to>devkitARM")
+$(error "Please set DEVKITPRO in your environment. export DEVKITPRO=<path to>devkitPro")
 endif
 
 include $(DEVKITPRO)/devkitA64/base_tools