No rule to make target 'doc/misc/modus-themes.texi', needed by 'info/dir'. Stop.

Hi!

I ~daily build emacs from git, in a highly parallel build. A couple
days ago the build started failing, most of the time, not always,
with:

/usr/pkg/bin/gmake actual-all || /usr/pkg/bin/gmake advice-on-failure make-target=all exit-status=$?
gmake[1]: Entering directory '/tmp/wip/emacs-git/work/emacs'
/usr/pkg/bin/gmake -C lib all
/usr/pkg/bin/gmake -C doc/lispref DOCLANG=default info
/usr/pkg/bin/gmake -C doc/lispintro DOCLANG=default info
/usr/pkg/bin/gmake -C doc/emacs DOCLANG=default info
gmake[1]: *** No rule to make target 'doc/misc/modus-themes.texi', needed by 'info/dir'.  Stop.
gmake[1]: *** Waiting for unfinished jobs....
gmake[2]: Entering directory '/tmp/wip/emacs-git/work/emacs/doc/lispref'
mkdir -p ../../info
gmake[2]: Entering directory '/tmp/wip/emacs-git/work/emacs/doc/lispintro'
mkdir -p ../../info
gmake[2]: Entering directory '/tmp/wip/emacs-git/work/emacs/doc/emacs'
mkdir -p ../../info

I suspect this rule in lisp/Makefile.in:

org-manuals: main-first
        $(AM_V_at)$(MAKE) -C ../doc/misc org.texi modus-themes.texi

is not parallel-make-safe-enough, but I don't have a fix.

Does anyone else have one?

Thanks,
 Thomas