title: "-std=gnu++0x"option for MacOS
body: <p>I'm trying to compile a CMake project which uses </p>
  
  <pre><code>set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} "-Wall -std=gnu++0x")
  </code></pre>
  
  <p>in the CMakeLists.txt file under MacOS X Lion. I have installed XCode 4.2.1. but the compiler fails with this:</p>
  
  <pre><code>cd something/src/lib &amp;&amp; /usr/bin/c++   -Dlib_ginacra_EXPORTS -Wall -std=gnu++0x -fPIC   -o CMakeFiles/lib_ginacra.dir/utilities.cpp.o -c something/src/lib/utilities.cpp
  cc1plus: error: unrecognized command line option "-std=gnu++0x"
  </code></pre>
  
  <p>The compiler's verion is:</p>
  
  <pre><code>c++ --version
  i686-apple-darwin11-llvm-g++-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.1.00)
  </code></pre>