Implement SIMD latest opcodes and update LLVM to 13.0 (#758)

Implement the latest SIMD opcodes and update LLVM 13.0,
update the llvm build scripts, update the sample workloads‘ build scripts,
and build customized wasi-sdk to build some workloads.
Also refine the CI rules.

Signed-off-by: Wenyong Huang <wenyong.huang@intel.com>

samples/workload/README.md

@@ -1,5 +1,5 @@
 All workloads have similar requirment of software dependencies, including
-**wasi-sdk**, **emsdk**, **wabt** and **binaryen**
+**emsdk**, **wabt** and **binaryen**
 
 > There might be slight differences when using MacOS and other Linux distro than Ubuntu. This document only target
 Ubuntu 18.04 as example.
@@ -10,16 +10,6 @@ use [preparation.sh](./preparation.sh) to install all dependencies before compil
 
 for details, the script includes below steps:
 
-- **wasi-sdk**. Install
-  [latest release](https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-12/wasi-sdk-12.0-linux.tar.gz)
-  to */opt/wasi-sdk*
-
-``` bash
-$ wget https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-${WASI_SDK_VER}/${WASI_SDK_FILE}
-$ tar zxf ${WASI_SDK_FILE} -C /opt
-$ ln -sf /opt/wasi-sdk-${WASI_SDK_VER}.0 /opt/wasi-sdk
-```
-
 - **wabt**. Install
   [latest release](https://github.com/WebAssembly/wabt/releases/download/1.0.23/wabt-1.0.23-ubuntu.tar.gz)
   to */opt/wabt*
@@ -32,15 +22,15 @@ $ ln -sf /opt/wabt-${WABT_VER} /opt/wabt
 
 - **emsdk**. Refer to [the guide](https://emscripten.org/docs/getting_started/downloads.html). Don't forget to activate
   emsdk and set up environment variables. Verify it with `echo ${EMSDK}`. Please be sure to install and activate the building
-  of 2.0.12
+  of 2.0.26
 
 ``` bash
 $ cd /opt
 $ git clone https://github.com/emscripten-core/emsdk.git
 $ cd emsdk
 $ git pull
-$ ./emsdk install 2.0.12
-$ ./emsdk activate 2.0.12
+$ ./emsdk install 2.0.26
+$ ./emsdk activate 2.0.26
 $ echo "source /opt/emsdk/emsdk_env.sh" >> "${HOME}"/.bashrc
 ```