Add xtensa AOT support and fix build issue of alios (#223)

* Clean compiling warnings of zephyr samples

* Support xtensa AOT and fix build issue of alios

wamr-compiler/build_llvm_xtensa.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+
+# Copyright (C) 2019 Intel Corporation. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+DEPS_DIR=${PWD}/../core/deps
+
+cd ${DEPS_DIR}
+if [ ! -d "llvm" ]; then
+  echo "Clone llvm Xtensa to core/deps/ .."
+  git clone https://github.com/espressif/llvm-project.git llvm
+fi
+
+cd llvm
+mkdir -p build
+cd build
+
+if [ ! -f bin/llvm-lto ]; then
+
+  CORE_NUM=$(nproc --all)
+  if [ -z "${CORE_NUM}" ]; then
+    CORE_NUM=1
+  fi
+
+  echo "Build llvm with" ${CORE_NUM} "cores"
+
+  cmake ../llvm \
+          -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
+          -DCMAKE_BUILD_TYPE:STRING="Release" \
+          -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD:STRING="Xtensa" \
+          -DLLVM_BUILD_LLVM_DYLIB:BOOL=OFF \
+          -DLLVM_OPTIMIZED_TABLEGEN:BOOL=ON \
+          -DLLVM_INCLUDE_EXAMPLES:BOOL=OFF \
+          -DLLVM_INCLUDE_TESTS:BOOL=OFF \
+          -DLLVM_INCLUDE_BENCHMARKS:BOOL=OFF \
+          -DLLVM_APPEND_VC_REV:BOOL=OFF
+  make -j ${CORE_NUM}
+
+else
+  echo "llvm has already been built"
+fi
+
+cd ${PWD}
+

wamr-compiler/main.c

@@ -14,7 +14,7 @@ print_help()
 {
   printf("Usage: wamrc [options] -o output_file wasm_file\n");
   printf("  --target=<arch-name>      Set the target arch, which has the general format: <arch><sub>\n");
-  printf("                            <arch> = x86_64, i386, aarch64, arm, thumb, mips.\n");
+  printf("                            <arch> = x86_64, i386, aarch64, arm, thumb, xtensa, mips.\n");
   printf("                              Default is host arch, e.g. x86_64\n");
   printf("                            <sub> = for ex. on arm or thumb: v5, v6m, v7a, v7m, etc.\n");
   printf("                            Use --target=help to list supported targets\n");