Improve documentation for compiler_gym.util.flags module.
# Common flag definitions for command line usage
-This directory contains modules that define command line flags for use in
-scripts. These modules should not be used by the core library as they may
-interfere with user code.
+This directory contains modules that define command line flags for use by
+`compiler_gym.bin` and other scripts. The reason for defining flags here is to
+allow flag names to be re-used across scripts without causing
+multiple-definition errors when the scripts are imported.
+
+Using these flags requires that the absl flags library is initialized. As such
+they should not be used in the core library.
