--- Makefile.orig	2014-03-23 10:09:16 UTC
+++ Makefile
@@ -17,7 +17,7 @@ installdir  = $(addprefix $(DESTDIR), $(
 MOD_CXXFLAGS = $(PIC) $(shell pkg-config pure --cflags) $(CFLAGS) $(CPPFLAGS)
 MOD_LDFLAGS = $(shell pkg-config pure --libs) $(LDFLAGS)
 
-CFLAGS = -g -O2 -Wall -Wextra
+CFLAGS ?= -g -O2 -Wall -Wextra
 
 ifeq "$(DLL)" ".dylib"
 DLL_FLAGS = -install_name "$(libdir)/pure/$@"