--- lib/surf/Makefile.orig	2022-11-15 15:32:58 UTC
+++ lib/surf/Makefile
@@ -6,7 +6,7 @@ INCLUDE     = -I. 
 LINCLUDE    = -lm
 OPT_CFLAGS  = -O2 $(FLAGS) $(INCLUDE)
 #CFLAGS	    = -g $(FLAGS) $(INCLUDE)
-CFLAGS	    = -O2 $(FLAGS) $(INCLUDE)
+CFLAGS	    += -O2 $(FLAGS) $(INCLUDE)
 
 # These are the user object files in the application
 SRCS        = surf.c io.c compute.c dual.c utils.c lp.c chull.c tessel_cases.c \