title: Cmake : how to append string to the variable via command line?
body: <p>In my CMakeList.txt i can do the following thing: </p>
  
  <pre><code>set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -new -flags -here")
  </code></pre>
  
  <p>Is it possible to to the same thing via command line? Like: </p>
  
  <pre><code>cmake.exe -DCMAKE_CXXFLAGS+= -new -flags
  </code></pre>