Add warning message if Config doesn't exist

Makefile

@@ -41,6 +41,13 @@ endif
 
 all: headers uClibc_config.h subdirs $(DO_SHARED) done
 
+Config:
+	@echo
+	@echo "You didn't read the README, did you... =)"
+	@echo "Choose a configuration file in extras/Config/ and copy it to ./Config."
+	@echo
+	@exit 1
+
 shared:
 	@$(MAKE) -C libc shared
 ifeq ($(LDSO_PRESENT), $(TARGET_ARCH))