Fix unused parameters and variables

llvm-svn: 290459
diff --git a/libcxx/test/support/filesystem_test_helper.hpp b/libcxx/test/support/filesystem_test_helper.hpp
index 7150f79..c2e41fc 100644
--- a/libcxx/test/support/filesystem_test_helper.hpp
+++ b/libcxx/test/support/filesystem_test_helper.hpp
@@ -230,6 +230,7 @@
         // check that the fs test root in the enviroment matches what we were
         // compiled with.
         static bool checked = checkDynamicTestRoot();
+        ((void)checked);
         std::string cmd = LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER;
         cmd += " \"" + raw_cmd + "\"";
         int ret = std::system(cmd.c_str());