Test using sherpa-onnx as a cmake subproject (#1961)

.github/scripts/as-cmake-sub-project/main.cc

@@ -0,0 +1,10 @@
+#include "sherpa-onnx/csrc/offline-recognizer.h"
+#include "sherpa-onnx/csrc/parse-options.h"
+
+int main(int32_t argc, char *argv[]) {
+  sherpa_onnx::ParseOptions po("help info");
+  sherpa_onnx::OfflineRecognizerConfig config;
+  config.Register(&po);
+  po.PrintUsage();
+  return 0;
+}