title: How to set an Xcode attribute in CMake for a specific configuration?
body: <p>I'm using CMake to generate an Xcode project, and I use</p>
  
  <pre><code>set_target_properties(myproj PROPERTIES XCODE_ATTRIBUTE_WHATEVER "some value")
  </code></pre>
  
  <p>to explicitly set a build setting. I'd like to only set it for a particular configuration, similar to using</p>
  
  <pre><code>set(CMAKE_CXX_FLAGS_MYCONFIG "-O2")
  </code></pre>
  
  <p>How can I do this?</p>