> Thanks, but please capture and post here the complete build log, from
> its start till the last error message.  We need to see all of that to
> understand what could cause the problem.
>
> Adding Stefan who made that commit.


Looks pretty straightforward to me since cl-find-class is on cl-extra.el

https://github.com/emacs-mirror/emacs/blob/master/lisp/emacs-lisp/cl-extra.el#L738

which was removed by that commit:

$ git diff HEAD~1
diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
index bdc59703de9..7fd9543d2ba 100644
--- a/lisp/emacs-lisp/comp.el
+++ b/lisp/emacs-lisp/comp.el
@@ -29,10 +29,7 @@
 ;;; Code:

 (require 'bytecomp)
-(require 'cl-extra)
 (require 'cl-lib)
-(require 'cl-macs)
-(require 'cl-seq)
 (require 'gv)
 (require 'rx)
 (require 'subr-x)

Anyway, attached is the build log:

$ make -j 12 > build.txt 2>&1