--- a/Makefile
+++ b/Makefile
@@ -2,8 +2,8 @@
 
 all: longrun README stamp-po
 
-longrun: longrun.c
-	gcc -DLOCALEDIR=\"$(LOCALEDIR)\" -g -O2 -W -Wall -o longrun longrun.c
+CFLAGS += -W -Wall
+CPPFLAGS += -DLOCALEDIR=\"$(LOCALEDIR)\"
 
 README: longrun.1
 	groff -Tascii -man longrun.1 | col -bx > README