bug#55016: 28.1; xref-find-references finds no matches if project dir contains a space

[Eli Zaretskii]

> From: Peter Povinec <spepo.42@gmail.com>
> Date: Tue, 19 Apr 2022 10:06:28 -0700
> Cc: 55016@debbugs.gnu.org
> 
> The patch actually makes it worse. Now even the 'nospacedir' case fails
> the same way (steps 6 and 7 in my recipe).

Actually, one more idea: perhaps the quoting makes things first
because your file names begin with "~/"?  In that case, doing
something like this instead should do better:

   (shell-quote-argument (expand-file-name rootdir))