title: Porting CMake to OS X Yosemite
body: <p>I am trying to update my Macport for Yosemite and installation of cmake fails.
  Here's the log file:</p>
  
  <pre><code>:info:configure CMake Error at Modules/Platform/Darwin.cmake:213 (message):
  :info:configure   CMAKE_OSX_DEPLOYMENT_TARGET is '10.10' but CMAKE_OSX_SYSROOT:
  :info:configure 
  :info:configure    ""
  :info:configure 
  :info:configure   is not set to a MacOSX SDK with a recognized version.  Either set
  :info:configure   CMAKE_OSX_SYSROOT to a valid SDK or set CMAKE_OSX_DEPLOYMENT_TARGET to empty.
  </code></pre>