Move a ref-counted pointer instead of copying it. NFC.

llvm-svn: 328623
diff --git a/clang/lib/Tooling/Tooling.cpp b/clang/lib/Tooling/Tooling.cpp
index caaf3aa..0644066 100644
--- a/clang/lib/Tooling/Tooling.cpp
+++ b/clang/lib/Tooling/Tooling.cpp
@@ -361,7 +361,7 @@
                      IntrusiveRefCntPtr<vfs::FileSystem> BaseFS)
     : Compilations(Compilations), SourcePaths(SourcePaths),
       PCHContainerOps(std::move(PCHContainerOps)),
-      OverlayFileSystem(new vfs::OverlayFileSystem(BaseFS)),
+      OverlayFileSystem(new vfs::OverlayFileSystem(std::move(BaseFS))),
       InMemoryFileSystem(new vfs::InMemoryFileSystem),
       Files(new FileManager(FileSystemOptions(), OverlayFileSystem)) {
   OverlayFileSystem->pushOverlay(InMemoryFileSystem);