[TestSupport] Remove old popen call
[TestSupport] Remove old popen call

This got left behind because of #if Xcode

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