Implement atomic and memset/memmove/memcpy intrinsic for riscv (#841)

- Lower aotmic instruction to non-atomic form on some platforms
- Lower memset/memmove/memcpy for XIP
- Disable rtti in cmake

core/iwasm/compilation/iwasm_compl.cmake

@@ -16,3 +16,11 @@ endif()
 
 set (IWASM_COMPL_SOURCE ${source_all})
 
+# Disalbe rtti to works with LLVM
+
+if (MSVC)
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /GR-")
+else()
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+endif()
+