bug#61867: dirstamp pattern rule kills buildability with FreeBSD make, NetBSD make, AIX make

[Karl Berry]

    I guess that the commit "dirstamp: switch to a pattern rule" is the culprit.
    
https://git.savannah.gnu.org/gitweb/?p=automake.git;a=commitdiff;h=55f8fcfd08cbf15d65d61dd2db934b6c3171cf06

Thanks Bruno. I reverted (attempted to, anyway) that change.
Hope it flies. Closing this, in hopes ... -k