Use correct Firebird SQL in tests

Author: tontonsb

ext/pdo/tests/pdo_039.phpt

@@ -6,7 +6,6 @@ pdo
 <?php
 $dir = getenv('REDIR_TEST_DIR');
 if (false == $dir) die('skip no driver');
-if (str_starts_with(getenv('PDOTEST_DSN'), "firebird")) die('xfail firebird driver does not behave as expected');
 require_once $dir . 'pdo_test.inc';
 PDOTest::skip();
 ?>
@@ -35,6 +34,9 @@ $query = 'SELECT 1';
 if ($conn->getAttribute(PDO::ATTR_DRIVER_NAME) === 'oci') {
     $query .= ' FROM DUAL';
 }
+if ($conn->getAttribute(PDO::ATTR_DRIVER_NAME) === 'firebird') {
+    $query .= ' FROM FROM RDB$DATABASE';
+}
 var_dump($conn->errorCode());
 var_dump($conn->errorCode());