There is a bug in emacs.install that breaks the creation of an info dir file with the emacs info files included in it. TL;DR: change ${INFO_FILES[@] for "${INFO_FILES[@]".

Info dir generation uses an array of file names and then uses it without double-quoting the array. If the array is not enclosed in double-quotes. it yields a very long and useless string instead of a list of quoted strings. As per "(bash.info.gz)Shell Parameter Expansion":

${!NAME[@]}
${!NAME[*]}
If NAME is an array variable, expands to the list of array indices
(keys) assigned in NAME. If NAME is not an array, expands to 0 if
NAME is set and null otherwise. When `@' is used and the
expansion appears within double quotes, each key expands to a
separate word.

Been there, done that. :-)