Build Preparation Build task concurrency set to 30 via user default IDEBuildOperationMaxNumberOfConcurrentCompileTasks note: Using new build system note: Building targets in parallel note: Planning build note: Analyzing workspace note: Constructing build description note: Build preparation complete error: Multiple commands produce '/Users/omochi/work/swift-source/build/Xcode-ReleaseAssert+swift-DebugAssert/llvm-macosx-x86_64/include/llvm/Support': 1) CreateBuildDirectory /Users/omochi/work/swift-source/build/Xcode-ReleaseAssert+swift-DebugAssert/llvm-macosx-x86_64/include/llvm/Support 2) That command depends on command in Target 'llvm_vcsrevision_h' (project 'LLVM'): script phase “Generate include/llvm/Support”