Gate build tool code that wont build on windows <6.1

Author: plemarquand

assets/test/targets/Sources/BuildToolExecutableTarget/BuildToolExecutableTarget.swift

@@ -1,3 +1,4 @@
+#if !(os(Windows) && swift(<6.1))
 import Foundation
 
 @main
@@ -34,4 +35,5 @@ struct JSONFormat: Decodable {
 enum CodeGeneratorError: Error {
     case invalidArguments
     case invalidData
-}
+}
+#endif