Fix GH-20871: Improve error messages for invalid -d command-line options

Author: khaledalam

sapi/cli/tests/gh20871.phpt

@@ -9,10 +9,21 @@ $php = getenv('TEST_PHP_EXECUTABLE_ESCAPED');
 exec("$php -d 'foo=bar=asd' -r \"echo 'hello' . PHP_EOL;\" 2>&1", $output, $exit_code);
 print_r($output);
 
+echo "\n";
+
+exec("$php -d 'foo=bar!asd' -r \"echo 'world' . PHP_EOL;\" 2>&1", $output2, $exit_code2);
+print_r($output2);
+
 ?>
 --EXPECTF--
 Array
 (
     [0] => PHP:  syntax error, unexpected '=' in -d option on line 0
     [1] => hello
 )
+
+Array
+(
+    [0] => PHP:  syntax error, unexpected '!' in -d option on line 0
+    [1] => world
+)