Use the right compiler and flags when building makecrc.
--- crc/makefile.orig	2020-11-16 13:51:50.000000000 -0600
+++ crc/makefile	2020-11-16 13:55:27.000000000 -0600
@@ -16,7 +16,7 @@
 	./makecrc
 
 makecrc:	makecrc.o
-	cc -O -o makecrc makecrc.o
+	$(CC) $(CFLAGS) -o makecrc makecrc.o
 
 arc.o:	arc.c
 ccitt.o:	ccitt.c
