Bazel client: remove StartupFlag class hierarchy

It's simpler and faster to use strings.

PiperOrigin-RevId: 262122410
diff --git a/src/test/cpp/option_processor_test.cc b/src/test/cpp/option_processor_test.cc
index e9f09cb..504ea1c 100644
--- a/src/test/cpp/option_processor_test.cc
+++ b/src/test/cpp/option_processor_test.cc
@@ -14,6 +14,8 @@
 
 #include "src/main/cpp/option_processor.h"
 
+#include <memory>
+
 #include "src/main/cpp/bazel_startup_options.h"
 #include "src/main/cpp/blaze_util.h"
 #include "src/main/cpp/blaze_util_platform.h"