TestFileHandle: Fix NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT

Author: spevans

TestFoundation/TestFileHandle.swift

@@ -9,6 +9,14 @@
 
 #if !DARWIN_COMPATIBILITY_TESTS // Disable until Foundation has the new FileHandle API
 
+#if NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT
+    #if canImport(SwiftFoundation) && !DEPLOYMENT_RUNTIME_OBJC
+        @testable import SwiftFoundation
+    #else
+        @testable import Foundation
+    #endif
+#endif
+
 import Dispatch
 
 class TestFileHandle : XCTestCase {