Build fix: TestPipe

Author: Lily Vulcano

Foundation/FileHandle.swift

@@ -57,7 +57,7 @@ open class FileHandle : NSObject {
         precondition(_handle != INVALID_HANDLE_VALUE, "Invalid file handle")
     }
 
-    private var _isPlatformHandleValid: Bool {
+    internal var _isPlatformHandleValid: Bool {
         return _handle != INVALID_HANDLE_VALUE
     }
 #else
@@ -71,7 +71,7 @@ open class FileHandle : NSObject {
         precondition(_fd >= 0, "Bad file descriptor")
     }
 
-    private var _isPlatformHandleValid: Bool {
+    internal var _isPlatformHandleValid: Bool {
         return fileDescriptor >= 0
     }
 #endif

TestFoundation/TestPipe.swift

@@ -7,6 +7,14 @@
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //
 
+#if NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT
+    #if canImport(SwiftFoundation) && !DEPLOYMENT_RUNTIME_OBJC
+        @testable import SwiftFoundation
+    #else
+        @testable import Foundation
+    #endif
+#endif
+
 #if !DARWIN_COMPATIBILITY_TESTS     // Disable until Foundation has the new FileHandle API
 class TestPipe: XCTestCase {