Do pass explicit empty argument to `-XCTest` (#3631)
Do pass explicit empty argument to `-XCTest` (#3631)

Right now if no tests are matching after filter/skip/etc, we pass no argument to `XCTest` which actually crashes the `xctest` CLI. This makes it so we instead pass an explicit empty argument to it.
apple/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager