Create a placeholder for WASI threads implementation (#1783)

This a simpler version of the PR: https://github.com/bytecodealliance/wasm-micro-runtime/pull/1638

samples/wasi-threads/wasm-apps/CMakeLists.txt

@@ -0,0 +1,29 @@
+# Copyright (C) 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+if (NOT DEFINED WASI_SDK_DIR)
+  set (WASI_SDK_DIR               "/opt/wasi-sdk")
+endif ()
+
+set (CMAKE_SYSROOT                  "${WASI_SYSROOT}")
+set (CMAKE_C_COMPILER               "${WASI_SDK_DIR}/bin/clang")
+set (CMAKE_C_COMPILER_TARGET        "wasm32-wasi")
+
+function (compile_sample SOURCE_FILE)
+  get_filename_component (FILE_NAME ${SOURCE_FILE} NAME_WLE)
+  set (WASM_MODULE ${FILE_NAME}.wasm)
+  add_executable (${WASM_MODULE} ${SOURCE_FILE})
+
+  target_compile_options (${WASM_MODULE} PRIVATE
+    -pthread -ftls-model=local-exec)
+
+  target_link_options (${WASM_MODULE} PRIVATE
+    -z stack-size=32768
+    LINKER:--export=__heap_base
+    LINKER:--export=__data_end
+    LINKER:--shared-memory,--max-memory=1966080
+    LINKER:--export=wasi_thread_start
+  )
+endfunction ()
+
+compile_sample(no_pthread.c)

samples/wasi-threads/wasm-apps/no_pthread.c

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2022 Amazon.com Inc. or its affiliates. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+#ifndef __wasi__
+#error This example only compiles to WASM/WASI target
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <wasi/api.h>
+
+static const int64_t SECOND = 1000 * 1000 * 1000;
+
+typedef struct {
+    int th_ready;
+    int value;
+} shared_t;
+
+__attribute__((export_name("wasi_thread_start"))) void
+wasi_thread_start(int thread_id, int *start_arg)
+{
+    shared_t *data = (shared_t *)start_arg;
+
+    printf("New thread ID: %d, starting parameter: %d\n", thread_id,
+           data->value);
+
+    data->value += 8;
+    printf("Updated value: %d\n", data->value);
+
+    data->th_ready = 1;
+    __builtin_wasm_memory_atomic_notify(&data->th_ready, 1);
+}
+
+int
+main(int argc, char **argv)
+{
+    shared_t data = { 0, 52 };
+    __wasi_errno_t err;
+
+    err = __wasi_thread_spawn(&data);
+    if (err != __WASI_ERRNO_SUCCESS) {
+        printf("Failed to create thread: %d\n", err);
+        return EXIT_FAILURE;
+    }
+
+    if (__builtin_wasm_memory_atomic_wait32(&data.th_ready, 0, SECOND) == 2) {
+        printf("Timeout\n");
+        return EXIT_FAILURE;
+    }
+
+    printf("Thread completed, new value: %d\n", data.value);
+
+    return EXIT_SUCCESS;
+}