bpf_glue: include errno.h

If __NR_bpf is not enabled, bpf() function set errno and return -1. Thus,
this patch includes the header.

Fixes: ac4e0913be ("bpf: Export bpf syscall wrapper")
Signed-off-by: Juhee Kang <claudiajkang@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

lib/bpf_glue.c

@@ -7,6 +7,7 @@
 #include <sys/syscall.h>
 #include <limits.h>
 #include <unistd.h>
+#include <errno.h>
 
 #include "bpf_util.h"
 #ifdef HAVE_LIBBPF