I said:
> The problem was that I already had bison output files built in the
> source tree. If I remove those, the build goes through (with bison
> output files built in the object tree).
I have to take that back: the bison outputs are rebuilt in the source
tree, as indeed they should be. I'm now fairly confused about why
the first build attempt failed and the second succeeded. The failure
occurred on a machine running gmake 3.78.1 ... maybe this is some
bug in that version of make? I can't reproduce any problem on a machine
running gmake 3.79.1...
regards, tom lane