Disambiguate getsockname() call.

src/node-capnp/capnp.cc

@@ -570,7 +570,7 @@ public:
       struct sockaddr_in6 inet6;
     } addr;
     addrlen = sizeof(addr);
-    KJ_SYSCALL(getsockname(fd, &addr.generic, &addrlen));
+    KJ_SYSCALL(::getsockname(fd, &addr.generic, &addrlen));
     switch (addr.generic.sa_family) {
       case AF_INET: return ntohs(addr.inet4.sin_port);
       case AF_INET6: return ntohs(addr.inet6.sin6_port);