Fix libresolv initialization

Fixes: 9533031891c0 ("Update libresolv usage")

Signed-off-by: Youfu Zhang <[email protected]>

dns/transport/local/resolv_darwin_cgo.go

@@ -20,8 +20,8 @@ import (
 )
 
 func dnsReadConfig(_ context.Context, _ string) *dnsConfig {
-	var state C.res_state
-	if C.res_ninit(state) != 0 {
+	var state C.struct___res_state
+	if C.res_ninit(&state) != 0 {
 		return &dnsConfig{
 			servers:  defaultNS,
 			search:   dnsDefaultSearch(),

dns/transport/local/resolv_test.go

@@ -0,0 +1,13 @@
+package local
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestDNSReadConfig(t *testing.T) {
+	t.Parallel()
+	require.NoError(t, dnsReadConfig(context.Background(), "/etc/resolv.conf").err)
+}