References:
 <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10444>
 <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10448>

And here is a two-patch series fixing the bug.  The first patch enhances
the testsuite coverage for the various `dist-*' options and formats and
for the "make dist" usages (and in doing so exposes the bug), the second
patch fixes the problem (which, it turns out, was simply due to missing
edits after a merge).

Tested on Debian unstable (GNU make 3.81 and 3.80), Solaris 10 (with
GNU make 3.82, CCS make and Sun Distributed Make) and NetBSD 5.1 (with
system make and GNU make 3.82).

I will push the patches to master in a day or two if there is no objection.

Regards,
  Stefano