[Commands] Use user namespaced temporary directory
[Commands] Use user namespaced temporary directory

- <rdar://problem/34130627> [SR-5788]: SwiftPM uses global tmp directory
- https://bugs.swift.org/browse/SR-5788

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