Distinguish Different Development Platforms By QMake And CMake

We can use qmake to configure a project for different platforms after reading qt document, Qt 5 > qmake manual > Getting Started.
The qmake syntax:

macx{
    message("compile for mac os x")
    ICON = Images/logo.icns
}

win32{
    message("compile for windows")
    RC_ICONS = Images/logo.ico
}

Similarly, we can read the target system macro definition on CMake documentation and add settings on CMakeLists.txt to improve project compatibility.
CMake syntax:

if( WIN32 )
    message( "This is windows platform" )
else( UNIX )
    message( "This is Unix like system" )
    if( APPLE )
        message( "This is mac os x" )
    endif()
endif()