centos7 编译licode 报error: ‘alloc_size’ 错误

一、错误信息：

      centos7 编译licode时，libav 总是报alloc_size的错误，all warnings being treated as errors所有的警告都被当成了错误，这样就会无缘无故报很多错误。修改CMakeLists开启警告信息，不用把警告当错误。

libdeps/build/include/libavutil/mem.h:174:79: error: ‘alloc_size’ attribute ignored on a function returning ‘int’ [-Werror=attributes]

解决方法，打开文件src/erizo/CMakeLists.txt，找到CMAKE_CXX_FLAGS ，添加-Wno-error。

if(${ERIZO_BUILD_TYPE} STREQUAL "debug")
  message("Generating DEBUG project")
  set(CMAKE_CXX_FLAGS "-g -Wall  -std=c++14 ${ERIZO_CMAKE_CXX_FLAGS} -Wno-error")
elseif(${ERIZO_BUILD_TYPE} STREQUAL "sanitizer")
    message("Generating SANITIZER project")
    set(CMAKE_CXX_FLAGS "-g -Wall -std=c++14 ${ERIZO_CMAKE_CXX_FLAGS} -O1 -fno-omit-frame-pointer -fsanitize=address -fno-optimize-sibling-calls")
else()
  mes