[Automake-NG] Can we require GNU make >= 3.81? (make memoization doesn't work with GNU make 3.80)

[Stefano Lattarini]

I've just discovered that variable memoization, as we've carefully
and laboriously implemented it:

  <http://lists.gnu.org/archive/html/automake-ng/2012-05/msg00067.html>
  <http://lists.gnu.org/archive/html/automake-ng/2012-05/msg00076.html>

does not work with GNU make 3.80 :-(

Since GNU make 3.81 has been released by more than six years now, any
objection against requiring it as the minimal supported version?  I'd
rather not waste efforts on older versions used only by a vanishingly
small percentage of the user base ...

Note that sadly we can't require GNU make >= 3.82 (which would offer use
the .ONESHELL feature) because Debian and Ubuntu still comes with GNU make
3.81 as the only version available through the package manager :-(

Regards,
  Stefano