Fix corrupted external render content (#35946)

Fix #35944

tests/sqlite.ini.tmpl

@@ -122,7 +122,7 @@ RENDER_CONTENT_MODE = sanitized
 [markup.no-sanitizer]
 ENABLED = true
 FILE_EXTENSIONS = .no-sanitizer
-RENDER_COMMAND = echo '<script>window.alert("hi")</script>'
+RENDER_COMMAND = go run tools/test-echo.go
 ; This test case is reused, at first it is used to test "no-sanitizer" (sandbox doesn't take effect here)
 ; Then it will be updated and used to test "iframe + sandbox-disabled"
 RENDER_CONTENT_MODE = no-sanitizer