fix bug in clang++

CMakeLists.txt

@@ -76,8 +76,12 @@ add_definitions(-DENABLE_RTMP2RTSP -DENABLE_RTSP2RTMP -DENABLE_HLS)
 
 #引用头文件路径
 include_directories(${PROJECT_SOURCE_DIR}/src)
+
 #使能c++11
-add_compile_options(-std=c++11)
+if(CMAKE_COMPILER_IS_GNUCXX)
+    add_compile_options(-std=c++11)  
+endif(CMAKE_COMPILER_IS_GNUCXX)
+
 #关闭过期接口警告
 add_compile_options(-Wno-deprecated-declarations)
 #关闭__FUNCTION__宏在函数外警告