[SwiftTool] Display fixit for fixing invalid tools version
[SwiftTool] Display fixit for fixing invalid tools version

-- <rdar://problem/31888791> Diagnostic for swift-tools-version should show tools-version subcommand

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