Update build scripts for Windows, linux, support macos & 'build readme'

Remove the older shell scripts, they are superseede by a Makefile
which is more efficient.

BTW update the build README

src/build-scripts/build-native.sh

@@ -1,6 +0,0 @@
-#!/bin/bash
-set -e
-
-pushd ../java/argon2
-ndk-build
-popd