Add README for android libs. (#1693)

build-android-arm64-v8a.sh

@@ -150,6 +150,22 @@ cp -fv $onnxruntime_version/jni/arm64-v8a/libonnxruntime.so install/lib 2>/dev/n
 rm -rf install/share
 rm -rf install/lib/pkgconfig
 rm -rf install/lib/lib*.a
+if [ -f install/lib/libsherpa-onnx-c-api.so ]; then
+  cat >install/lib/README.md <<EOF
+# Introduction
+
+Note that if you use Android Studio, then you only need to
+copy libonnxruntime.so and libsherpa-onnx-jni.so
+to your jniLibs, and you don't need libsherpa-onnx-c-api.so or
+libsherpa-onnx-cxx-api.so.
+
+libsherpa-onnx-c-api.so and libsherpa-onnx-cxx-api.so are for users
+who don't use JNI. In that case, libsherpa-onnx-jni.so is not needed.
+
+In any case, libonnxruntime.is is always needed.
+EOF
+  ls -lh install/lib/README.md
+fi
 
 # To run the generated binaries on Android, please use the following steps.
 #