[Bootstrap] Install XCTest helper tool to bin.
[Bootstrap] Install XCTest helper tool to bin.

This will install the XCTest helper tool which lists tests on OSX in the
bin folder. Note that this will still not build the helper during stage1
which should be fine because its not really needed in stage1.

JGiola/swift-package-manager,vmanot/swift-package-manager,haskellswift/swift-package-manager,apple/swift-package-manager,haskellswift/swift-package-manager,apple/swift-package-manager,JGiola/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,mxcl/swift-package-manager,abertelrud/swift-package-manager,mxcl/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager,mxcl/swift-package-manager,haskellswift/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,sschiau/swift-package-manager,vmanot/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,sschiau/swift-package-manager,sschiau/swift-package-manager,JGiola/swift-package-manager,JGiola/swift-package-manager,mxcl/swift-package-manager,vmanot/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,JGiola/swift-package-manager