Fix GH-17797: zend_test_compile_string crash on invalid script path.

When looking for the last slash of the script path, it leads to
underflow being promoted to SIZE_MAX being way beyond MAXPATHLEN.

Author: devnexen

main/fopen_wrappers.c

@@ -603,7 +603,9 @@ PHPAPI zend_string *php_resolve_path(const char *filename, size_t filename_lengt
 		const char *exec_fname = ZSTR_VAL(exec_filename);
 		size_t exec_fname_length = ZSTR_LEN(exec_filename);
 
-		while ((--exec_fname_length < SIZE_MAX) && !IS_SLASH(exec_fname[exec_fname_length]));
+		do {
+			if (exec_fname_length == 0) break;
+		} while (!IS_SLASH(exec_fname[--exec_fname_length]));
 		if (exec_fname_length > 0 &&
 			filename_length < (MAXPATHLEN - 2) &&
 		    exec_fname_length + 1 + filename_length + 1 < MAXPATHLEN) {