The problem
seems to be introduced by the compiler optimization. When I add a debugging printout statement to print the option out before parsing it, the problem goes away -- even when the debug option is not invoked, so the printout never occurs!
I've seen stuff like this a few times before, but it is always peculiar. Anyway, I will start a rebuild and new binaries will be available by morning (Saturday, 28 Mar 2015 CE).