libc: Add __h_errno_location

This is needed to run iperf3.

https://github.com/cloudius-systems/osv/issues/305



Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

libc/build.mk

@@ -379,6 +379,7 @@ libc += network/inet_ntop.o
 libc += network/proto.o
 libc += network/if_indextoname.o
 libc += network/gai_strerror.o
+libc += network/h_errno.o
 
 libc += prng/rand.o
 libc += prng/random.o

libc/network/h_errno.c

+#include <netdb.h>
+
+#undef h_errno
+int h_errno;
+
+int *__h_errno_location(void)
+{
+        return &h_errno;
+}