xref in GNU ELPA broken on Emacs 26

[Yuri Khan]

Hello,

I foolishly did a M-x package-list-packages RET U x RET and got an
xref package version 1.3.0. It attempts to use the cl-defstruct option
:noinline, which is not supported in cl-macs.el that comes with Emacs
26.3 that comes with Ubuntu 20.04.

xref 1.3.0 declares dependency on Emacs 26.1.

I seem to have managed to repair my local installation by manually
downloading xref-1.2.1.tar.lz from the GNU ELPA site and telling
‘package-install-file’ to install from the directory I got by
unpacking it, then exiting Emacs and removing
~/.emacs.d/elpa/xref-1.3.0.