Did that -- I tried again with -Q, after having moved ~/.emacs.d/elpa to ~/.emacs.d/elpa.hid.
I then of course had to M-x list-packages RET and install ivy again; that turned out to get me ivy-0.12.0, so I updated the repro.el file to reflect that, then started over (with -Q of course); it did just the same thing.
I started over, this time using the same git commit as the system which worked -- that failed too! So it's clearly not emacs. I noticed that on the system that worked, "man -k ." yielded about 14000 lines of output, whereas on the system that failed, the same command yielded ".: nothing appropriate" ... so it's pretty likely that my "man" command is at fault, not Emacs.