Basics: introduce some native path representation helpers

We end up needing these in a few places, and while we could make it
`internal` and use `@testable` imports in the tests, this ends up being
needed in `Build` and `PackageLoading`.  Ideally, we would give it
package visibility, but that functionality would not be backwards
compatible.  This is a reluctant approach at solving that problem by
using `public` visibility.

Author: compnerd

Sources/Basics/NativePathExtensions.swift

@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import struct TSCBasic.AbsolutePath
+
+extension String {
+    public func nativePathString(escaped: Bool) -> Self {
+        return URL(fileURLWithPath: self).withUnsafeFileSystemRepresentation {
+            let repr = String(cString: $0!)
+            if escaped {
+                return repr.replacingOccurrences(of: "\\", with: "\\\\")
+            }
+            return repr
+        }
+    }
+}
+
+extension AbsolutePath {
+    public func nativePathString(escaped: Bool) -> String {
+        return self.pathString.nativePathString(escaped: escaped)
+    }
+}

Sources/Build/BuildPlan.swift

@@ -30,18 +30,6 @@ extension String {
     }
 }
 
-extension AbsolutePath {
-    internal func nativePathString(escaped: Bool) -> String {
-        return URL(fileURLWithPath: self.pathString).withUnsafeFileSystemRepresentation {
-            let repr = String(cString: $0!)
-            if escaped {
-                return repr.replacingOccurrences(of: "\\", with: "\\\\")
-            }
-            return repr
-        }
-    }
-}
-
 extension BuildParameters {
     /// Returns the directory to be used for module cache.
     public var moduleCache: AbsolutePath {