--- Makefile.orig	2015-10-15 21:25:02 UTC
+++ Makefile
@@ -2,11 +2,11 @@
 VERSION = 2.1
 
 #CC = gcc
-CPPFLAGS = -DVERSION_STR=\"$(VERSION)\"
-CFLAGS = -Wall -g
+CPPFLAGS += -DVERSION_STR=\"$(VERSION)\"
+CFLAGS ?= -Wall -g
 
 LD = $(CC)
-LDFLAGS = -g
+LDFLAGS ?= -g
 LDLIBS =
 
 all: picocom