--- Makefile.orig	2015-07-27 18:28:54 UTC
+++ Makefile
@@ -1,5 +1,5 @@
-CC=gcc
-CFLAGS= -W -O2 -Wall -Wno-self-assign -Wno-unused-function
+CC?=gcc
+CFLAGS?= -W -O2 -Wall -Wno-self-assign -Wno-unused-function
 DFLAGS= -D_FILE_OFFSET_BITS=64
 GLIBS=-lm
 GENERIC_SRC= string.h bitvec.h file_reader.h hashset.h sort.h list.h dna.h heap.h stdaln.h vector.h