Update build scripts and documents of workload samples for wasi-sdk-12.0 (#484)

Update the build scripts of sample workloads (meshoptimizer/bwa/wasm-av1) to use the wasi-sdk-12.0 firstly to build the workload and discard clang-11, as wasi-sdk-12 supports wasi, simd and pthread better. And update the related documents.
Also modify wasm mini loader to sync up with the change of wasm normal loader.

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

samples/workload/wasm-av1/CMakeLists.txt

@@ -5,6 +5,38 @@ cmake_minimum_required (VERSION 3.0)
 
 project(av1_wasm)
 
+################  WASI-SDK ################
+find_path(WASI_SDK_HOME
+  NAMES wasi-sdk
+  PATHS /opt/
+  REQUIRED
+)
+
+if (NOT WASI_SDK_HOME)
+  message(FATAL_ERROR
+    "can not find wasi-sdk. "
+    "please download it from "
+    "https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-12/wasi-sdk-12.0-linux.tar.gz "
+    "and install it under /opt/wasi-sdk"
+  )
+endif()
+
+#
+# check clang version
+execute_process(COMMAND
+  ${WASI_SDK_HOME}/wasi-sdk/bin/clang --version
+  OUTPUT_VARIABLE clang_full_version_string
+)
+string(REGEX REPLACE ".*clang version ([0-9]+\\.[0-9]+).*" "\\1"
+  CLANG_VERSION_STRING ${clang_full_version_string}
+)
+message("cur clang version is ${CLANG_VERSION_STRING}")
+if(CLANG_VERSION_STRING VERSION_LESS 11.0)
+  message(FATAL_ERROR
+    "please install latest wai-sdk to get a clang-11 at least"
+  )
+endif()
+
 ################  BINARYEN ################
 find_program(WASM_OPT
     NAMES wasm-opt
@@ -55,7 +87,10 @@ ExternalProject_Add(av1
                   && ${CMAKE_COMMAND} -E echo "Copying pre-installed CMakeLists.txt"
                   && ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/CMakeLists.avx_wasm.txt CMakeLists.txt
                   && git apply ../av1-clang.patch
-  CONFIGURE_COMMAND ${CMAKE_COMMAND} -DCMAKE_TOOLCHAIN_FILE=${CMAKE_CURRENT_SOURCE_DIR}/../cmake/toolchain.cmake ${CMAKE_CURRENT_SOURCE_DIR}/av1
+  CONFIGURE_COMMAND  ${CMAKE_COMMAND}
+                         -DWASI_SDK_PREFIX=${WASI_SDK_HOME}/wasi-sdk
+                         -DCMAKE_TOOLCHAIN_FILE=${WASI_SDK_HOME}/wasi-sdk/share/cmake/wasi-sdk.cmake
+                         ${CMAKE_CURRENT_SOURCE_DIR}/av1
   BUILD_COMMAND     make testavx_opt
   INSTALL_COMMAND   ${CMAKE_COMMAND} -E copy testavx.opt.wasm ${CMAKE_CURRENT_BINARY_DIR}/testavx.wasm
 )