title: SDK version for building swift?
body: <p>I am trying to build swift from the source (<a href="https://github.com/apple/swift" rel="nofollow">https://github.com/apple/swift</a>). However, it throws an error when building PhaseScriptExecution. Here is the error message:</p>
  
  <pre><code>&lt;unknown&gt;:0: error: Swift does not support the SDK 'MacOSX10.11.sdk'
  make: *** [/Users/yangwei/Git/build/Xcode-DebugAssert/swift-macosx-x86_64/stdlib/public/core/macosx/x86_64/Swift.o] Error 1
  
  ** BUILD FAILED **
  
  
  The following build commands failed:
  PhaseScriptExecution CMake\ Rules /Users/yangwei/Git/build/Xcode-DebugAssert/swift-macosx-x86_64/stdlib/public/core/Swift.build/Debug/add_custom_command_target-8e6e230f23a92c1cda79a3cf59140ab8-Swift.o.build/Script-4123DECAA170465EA6F4D9CC.sh
  (1 failure)
  </code></pre>
  
  <p>It seems to be a problem related to SDK version. Can anyone tell me which SDK version I should use? and how can I downgrade to the version?</p>
  
  <p>Thanks!</p>
  
  <p>Update:</p>
  
  <p>I noticed the version issue so I tried to checkout branch of swift-2.2 of swift and all other required projects. However, when I tried to build with command <code>utils/build-script -x</code>, it shows following error message: </p>
  
  <pre><code>make -f /Users/yangwei/Git/build/Xcode-DebugAssert/llvm-macosx-x86_64/CMakeScripts/ReRunCMake.make
  make[1]: *** No rule to make target '/Users/yangwei/Git/llvm/lib/DebugInfo/CodeView/CMakeLists.txt', needed by '/Users/yangwei/Git/build/Xcode-DebugAssert/llvm-macosx-x86_64/CMakeFiles/cmake.check_cache'.  Stop.
  make: *** [/Users/yangwei/Git/build/Xcode-DebugAssert/llvm-macosx-x86_64/CMakeFiles/ZERO_CHECK] Error 2
  Command /bin/sh failed with exit code 2
  ** BUILD FAILED **
  
  The following build commands failed:
  PhaseScriptExecution CMake\ Rules /Users/yangwei/Git/build/Xcode-DebugAssert/llvm-macosx-x86_64/LLVM.build/Debug/ZERO_CHECK.build/Script-80DAA73EAB654B0EA77D1AEF.sh
  (1 failure)
  utils/build-script: command terminated with a non-zero exit status 65, aborting
  </code></pre>