Some wamr-ide improvements (#1354)

including:
- enable macOS support
- documentation improvements
- fix some warnings

test-tools/wamr-ide/WASM-Toolchain/Docker/build_docker_image.sh

@@ -1,9 +1,8 @@
+#!/bin/bash
+
 # Copyright (C) 2019 Intel Corporation.  All rights reserved.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#!/bin/bash
-docker pull gcc:9.3.0
-docker pull ubuntu:20.04
 docker build -t wasm-toolchain:1.0 .
 
 # delete intermediate docker image