add coverage flags for old gcc version
add coverage flags for old gcc version

waruqi/xmake,tboox/xmake,tboox/xmake,waruqi/xmake,waruqi/xmake,waruqi/xmake,waruqi/xmake,tboox/xmake,tboox/xmake,tboox/xmake,tboox/xmake,waruqi/xmake,waruqi/xmake,tboox/xmake