Do not compile HeadlessTerminal on Windows as it uses LocalProcess, we should upgrade at some point to the new subprocess API in Swift

Author: migueldeicaza

Sources/SwiftTerm/HeadlessTerminal.swift

@@ -4,7 +4,7 @@
 //
 //  Created by Miguel de Icaza on 4/5/20.
 //
-#if !os(iOS)
+#if !os(iOS) && !os(Windows)
 import Foundation
 
 ///