Fix memory leak in a unit test.

llvm-svn: 291595
diff --git a/llvm/unittests/Support/TarWriterTest.cpp b/llvm/unittests/Support/TarWriterTest.cpp
index dfcf88f..4a08883 100644
--- a/llvm/unittests/Support/TarWriterTest.cpp
+++ b/llvm/unittests/Support/TarWriterTest.cpp
@@ -49,7 +49,7 @@
   EXPECT_TRUE((bool)TarOrErr);
   std::unique_ptr<TarWriter> Tar = std::move(*TarOrErr);
   Tar->append(Filename, "contents");
-  Tar.release();
+  Tar.reset();
 
   // Read the tar file.
   ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = MemoryBuffer::getFile(Path);