Supports cmake compilation compatible with v3.13. (#340)

Co-authored-by: chenyu <cheny65@chinatelecom.cn>

@@ -144,7 +144,7 @@ endif()
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/Modules)
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
 
-if(NOT BUILD_SHARED_LIBS AND LINUX AND NOT APPLE)
+if(NOT BUILD_SHARED_LIBS AND CMAKE_SYSTEM_NAME STREQUAL Linux)
   if(SHERPA_ONNX_LINK_LIBSTDCPP_STATICALLY)
     message(STATUS "Link libstdc++ statically")
     set(CMAKE_CXX_FLAGS " ${CMAKE_CXX_FLAGS} -static-libstdc++ -static-libgcc ")

@@ -122,7 +122,7 @@ if(SHERPA_ONNX_ENABLE_CHECK)
   endif()
 endif()
 
-if(NOT BUILD_SHARED_LIBS AND LINUX AND NOT APPLE)
+if(NOT BUILD_SHARED_LIBS AND CMAKE_SYSTEM_NAME STREQUAL Linux)
   target_link_libraries(sherpa-onnx-core -pthread -ldl)
 endif()