> Can you check in the build log of 6kj7f8kz3h5fizir8l7nrxgras2ns3ww-m4-1.4.16
> what the line “checking which shell to use for syscmd” says?  (Remember
> that build logs are kept in /nix/var/log/nix/drvs or similar, depending
> on your localstatedir.  Make sure the value passed to --prefix in that
> log matches the one above.)

There were no logs.  So I ran 'nix-store --delete 6*w-m4-1.4.16', then
reinstalled it, and 'bison' succeeded.

Nikita