bug#32352: 27.0.50; build error

[Glenn Morris]

I seem to be able to reproduce it at will with (after a bootstrap):

touch lisp/files.el src/emacs.c 
rm src/bootstrap-emacs
make

which dies doing

./src/bootstrap-emacs -batch -f batch-byte-compile lisp/files.el

at (alist-get class dir-locals-class-alist) when gv.elc loads.
(It's fine if you load bytecomp.el instead of .elc.)

See also
http://lists.gnu.org/r/emacs-devel/2018-11/msg00156.html