Include <err.h>. On my system CVS Make(1) has an implicit declaration of

warnc(3) without it.

usr.bin/make/job.c

@@ -118,6 +118,7 @@ __FBSDID("$FreeBSD$");
 #endif
 #include <sys/wait.h>
 #include <ctype.h>
+#include <err.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>