fix compiling fuzz test under Linux after merging contrib to main repo

contrib/ports/unix/port/sys_arch.c

@@ -752,6 +752,7 @@ sys_arch_unprotect(sys_prot_t pval)
 }
 #endif /* SYS_LIGHTWEIGHT_PROT */
 
+#if !NO_SYS
 /* get keyboard state to terminate the debug app by using select */
 int
 lwip_unix_keypressed(void)
@@ -762,3 +763,4 @@ lwip_unix_keypressed(void)
   FD_SET(0, &fds);
   return select(1, &fds, NULL, NULL, &tv);
 }
+#endif /* !NO_SYS */

test/fuzz/Makefile

@@ -37,7 +37,8 @@ LDFLAGS=-lm
 # use 'make D=-DUSER_DEFINE' to pass a user define to gcc
 CFLAGS=-O0 $(D)
 
-CONTRIBDIR=../../../lwip-contrib
+LWIPDIR=../../src
+CONTRIBDIR=../../contrib
 include $(CONTRIBDIR)/ports/unix/Common.mk
 
 clean: