add spawn thread API and sample (#333)

samples/spawn-thread/wasm-apps/CMakeLists.txt

@@ -0,0 +1,34 @@
+# Copyright (C) 2019 Intel Corporation.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+cmake_minimum_required(VERSION 2.8)
+project(wasm-apps)
+
+set(WAMR_ROOT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../..)
+
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR wasm32)
+set (CMAKE_SYSROOT                  ${WAMR_ROOT_DIR}/wamr-sdk/app/libc-builtin-sysroot)
+
+if (NOT DEFINED WASI_SDK_DIR)
+    set (WASI_SDK_DIR               "/opt/wasi-sdk")
+endif ()
+
+set (CMAKE_C_FLAGS                  "-nostdlib -pthread -Qunused-arguments")
+set (CMAKE_C_FLAGS                  "${CMAKE_C_FLAGS} -z stack-size=32768")
+set (CMAKE_C_COMPILER_TARGET        "wasm32")
+set (CMAKE_C_COMPILER               "${WASI_SDK_DIR}/bin/clang")
+
+set (DEFINED_SYMBOLS
+"${WAMR_ROOT_DIR}/wamr-sdk/app/libc-builtin-sysroot/share/defined-symbols.txt")
+
+set (CMAKE_EXE_LINKER_FLAGS
+    "-Wl,--shared-memory,--max-memory=131072,       \
+    -Wl,--no-entry,--strip-all,--export=sum,        \
+    -Wl,--export=__heap_base,--export=__data_end    \
+    -Wl,--export=__wasm_call_ctors  \
+    -Wl,--allow-undefined-file=${DEFINED_SYMBOLS}"
+)
+
+add_executable(test.wasm  sum.c)
+target_link_libraries(test.wasm)

samples/spawn-thread/wasm-apps/sum.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+int sum(int start, int length)
+{
+    int sum = 0, i;
+
+    for (i = start; i < start + length; i++) {
+        sum += i;
+    }
+
+    return sum;
+}