Kludge include.am to work with automake <1.12

The SH_LOG_COMPILER feature doesn't work with older automakes, and
those are still in use in many environments we want to support
development on, like Debian Stable.

Instead, use autoconf substitution to fill out the shebang lines on
the shell scripts, and an intermediate make target to make them
executable.

This is a bugfix on the patches for #15344.  Bug not in any released
tor.