crypto/x509: better debug output for verify-cert calls

Now that pkix.Name offers String() we should use that as some CN's are blank.

Updates #24084

Change-Id: I268196f04b98c2bd4d5d0cf1fecd2c9bafeec0f1
Reviewed-on: https://go-review.googlesource.com/121357Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/crypto/x509/root_darwin.go

@@ -181,12 +181,12 @@ func verifyCertWithSystem(block *pem.Block, cert *Certificate) bool {
 	}
 	if err := cmd.Run(); err != nil {
 		if debugExecDarwinRoots {
-			println(fmt.Sprintf("crypto/x509: verify-cert rejected %s: %q", cert.Subject.CommonName, bytes.TrimSpace(stderr.Bytes())))
+			println(fmt.Sprintf("crypto/x509: verify-cert rejected %s: %q", cert.Subject, bytes.TrimSpace(stderr.Bytes())))
 		}
 		return false
 	}
 	if debugExecDarwinRoots {
-		println(fmt.Sprintf("crypto/x509: verify-cert approved %s", cert.Subject.CommonName))
+		println(fmt.Sprintf("crypto/x509: verify-cert approved %s", cert.Subject))
 	}
 	return true
 }