[Basic] Make ProcessResult publicly initable.
[Basic] Make ProcessResult publicly initable.

 - This is a useful general purpose type for encapsulating a terminated process'
   state, so it is reasonable for clients to be able to create instances (useful
   for testing, for example).

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