title: CMake Error: Could not create named generator XCode
body: <p>i have checked out llvm/clang/compiler-rt sources from official git repositories, but i'm having:</p>
  
  <pre><code>MBA-Anton:llvm_34_xcode_build asmirnov$ cmake -G XCode ../llvm_34
  CMake Error: Could not create named generator XCode
  </code></pre>
  
  <p>LLVM sources:</p>
  
  <pre><code>MBA-Anton:llvm_34_xcode_build asmirnov$ ls ../llvm_34
  CMakeLists.txt      Makefile.common     cmake           llvm.spec.in
  CODE_OWNERS.TXT     Makefile.config.in  configure       projects
  CREDITS.TXT     Makefile.rules      docs            test
  LICENSE.TXT     README.txt      examples        tools
  LLVMBuild.txt       autoconf        include         unittests
  Makefile        bindings        lib         utils
  </code></pre>
  
  <p>Cmake version:</p>
  
  <pre><code>MBA-Anton:llvm_34_xcode_build asmirnov$ cmake -version
  cmake version 2.8.11.1
  </code></pre>
  
  <p>Xcode generator should be supported for this cmake version according to <a href="http://www.cmake.org/cmake/help/v2.8.8/cmake.html#section_Generators" rel="noreferrer">doc</a> and output:</p>
  
  <pre><code>MBA-Anton:llvm_34_xcode_build asmirnov$ cmake --help
  ...
  
  Generators
  
  The following generators are available on this platform:
    Unix Makefiles              = Generates standard UNIX makefiles.
    Ninja                       = Generates build.ninja files (experimental).
    Xcode                       = Generate Xcode project files.
    CodeBlocks - Ninja          = Generates CodeBlocks project files.
    CodeBlocks - Unix Makefiles = Generates CodeBlocks project files.
    Eclipse CDT4 - Ninja        = Generates Eclipse CDT 4.0 project files.
    Eclipse CDT4 - Unix Makefiles
                                = Generates Eclipse CDT 4.0 project files.
    KDevelop3                   = Generates KDevelop 3 project files.
    KDevelop3 - Unix Makefiles  = Generates KDevelop 3 project files.
    Sublime Text 2 - Ninja      = Generates Sublime Text 2 project files.
    Sublime Text 2 - Unix Makefiles
                                = Generates Sublime Text 2 project files.
  </code></pre>