Use default hidden visibility to build libc_dns.

Bug: 11156955
Change-Id: Ia443705f5fbee0681039d4480abc89850968f475
diff --git a/libc/include/resolv.h b/libc/include/resolv.h
index 36b93ee..c8899ed 100644
--- a/libc/include/resolv.h
+++ b/libc/include/resolv.h
@@ -37,6 +37,7 @@
 #include <netinet/in.h>
 
 __BEGIN_DECLS
+#pragma GCC visibility push(default)
 
 struct res_state;
 
@@ -52,6 +53,7 @@
 extern int dn_comp(const char*, u_char*, int, u_char**, u_char**);
 extern int dn_expand(const u_char*, const u_char*, const u_char*, char*, int);
 
+#pragma GCC visibility pop
 __END_DECLS
 
 #endif /* _RESOLV_H_ */