Add WASI ABI compatibility check for multi-module (#913)

Refer to https://github.com/WebAssembly/WASI/blob/main/design/application-abi.md
to check the WASI ABI compatibility:
- Command (main module) may export _start function with signature "()"
- Reactor (sub module) may export _initialize function with signature "()"
- _start and _initialize can not be exported at the same time
- Reactor cannot export _start function
- Command and Reactor must export memory

And
- Rename module->is_wasi_module to module->import_wasi_api
- Refactor wasm_loader_find_export()
- Remove MULTI_MODULE related codes from mini_loader
- Update multi-module samples
- Fix a "use-after-free" issue. Since we reuse the memory instance of sub module,
   just to protect it from freeing an imported memory instance

samples/multi-module/CMakeLists.txt

@@ -1,7 +1,7 @@
 # Copyright (C) 2019 Intel Corporation.  All rights reserved.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required (VERSION 2.8...3.16)
 project(multi_module)
 
 ################  runtime settings  ################
@@ -41,7 +41,7 @@ set(WAMR_BUILD_INTERP 1)
 set(WAMR_BUILD_AOT 0)
 set(WAMR_BUILD_JIT 0)
 set(WAMR_BUILD_LIBC_BUILTIN 1)
-set(WAMR_BUILD_LIBC_WASI 0)
+set(WAMR_BUILD_LIBC_WASI 1)
 set(WAMR_BUILD_MULTI_MODULE 1)
 
 # compiling and linking flags
@@ -66,8 +66,79 @@ add_library(vmlib STATIC ${WAMR_RUNTIME_LIB_SOURCE})
 ################  application related  ################
 
 ################ WASM MODULES
+include(ExternalProject)
+
+message(CHECK_START "Detecting WASI-SDK")
+if(NOT (DEFINED WASI_SDK_DIR OR DEFINED CACHE{WASI_SDK_DIR}))
+  find_path(WASI_SDK_PARENT
+    wasi-sdk
+    PATHS /opt
+    NO_DEFAULT_PATH
+    NO_CMAKE_FIND_ROOT_PATH
+  )
+  if(WASI_SDK_PARENT)
+    set(WASI_SDK_DIR ${WASI_SDK_PARENT}/wasi-sdk)
+  endif()
+endif()
+if(WASI_SDK_DIR)
+  message(CHECK_PASS "found")
+else()
+  message(CHECK_FAIL "not found")
+endif()
+
+message(CHECK_START "Detecting WASI_TOOLCHAIN_FILE at ${WASI_SDK_DIR}")
+find_file(WASI_TOOLCHAIN_FILE
+  wasi-sdk.cmake
+  PATHS "${WASI_SDK_DIR}/share/cmake"
+  NO_DEFAULT_PATH
+  NO_CMAKE_FIND_ROOT_PATH
+)
+if(WASI_TOOLCHAIN_FILE)
+  message(CHECK_PASS "found")
+else()
+  message(CHECK_FAIL "not found")
+endif()
+
+message(CHECK_START "Detecting WASI_SYS_ROOT at ${WASI_SDK_DIR}")
+find_path(WASI_SYS_ROOT
+  wasi-sysroot
+  PATHS "${WASI_SDK_DIR}/share"
+  NO_DEFAULT_PATH
+  NO_CMAKE_FIND_ROOT_PATH
+)
+if(WASI_SYS_ROOT)
+  message(CHECK_PASS "found")
+  set(WASI_SYS_ROOT ${WASI_SYS_ROOT}/wasi-sysroot)
+else()
+  message(CHECK_FAIL "not found")
+endif()
+
+if(NOT EXISTS ${WASI_SDK_DIR} OR NOT EXISTS ${WASI_TOOLCHAIN_FILE} OR NOT EXISTS ${WASI_SYS_ROOT})
+  message(FATAL_ERROR "Please set the absolute path of wasi-sdk with \'cmake -DWASI_SDK_HOME=XXX\'")
+else()
+  message(STATUS "WASI_SDK_DIR is ${WASI_SDK_DIR}")
+  message(STATUS "WASI_TOOLCHAIN_FILE is ${WASI_TOOLCHAIN_FILE}")
+  message(STATUS "WASI_SYS_ROOT is ${WASI_SYS_ROOT}")
+endif()
+
 # .c -> .wasm
-add_subdirectory(wasm-apps)
+ExternalProject_Add(WASM_MODULE
+  SOURCE_DIR         ${CMAKE_CURRENT_SOURCE_DIR}/wasm-apps
+  UPDATE_COMMAND     ""
+  PATCH_COMMAND      ""
+  CONFIGURE_COMMAND  ${CMAKE_COMMAND}
+                       -DWASI_SDK_PREFIX=${WASI_SDK_DIR}
+                       -DCMAKE_TOOLCHAIN_FILE=${WASI_TOOLCHAIN_FILE}
+                       -DCMAKE_SYSROOT=${WASI_SYS_ROOT}
+                       -S ${CMAKE_CURRENT_SOURCE_DIR}/wasm-apps
+  BUILD_COMMAND      ${CMAKE_COMMAND} --build .
+  INSTALL_COMMAND    ${CMAKE_COMMAND} -E copy
+                       ./mA.wasm ${CMAKE_CURRENT_SOURCE_DIR}/build/
+                       ./mB.wasm ${CMAKE_CURRENT_SOURCE_DIR}/build/
+                       ./mC.wasm ${CMAKE_CURRENT_SOURCE_DIR}/build/
+                       ./mD.wasm ${CMAKE_CURRENT_SOURCE_DIR}/build/
+                       ./mE.wasm ${CMAKE_CURRENT_SOURCE_DIR}/build/
+)
 
 ################ NATIVE
 include_directories(${CMAKE_CURRENT_LIST_DIR}/src)
@@ -75,7 +146,7 @@ include (${SHARED_DIR}/utils/uncommon/shared_uncommon.cmake)
 
 add_executable(multi_module src/main.c ${UNCOMMON_SHARED_SOURCE})
 
-add_dependencies(multi_module vmlib wasm-modules)
+add_dependencies(multi_module vmlib WASM_MODULE)
 
 # libraries
 target_link_libraries(multi_module PRIVATE vmlib -lpthread -lm)