We use a number of build slaves. Some are Windows, some are Linux.

On the Windows machines we'd like to script using Cygwin, but the shell setting
is a master configuration.

So shell can be set to /bin/sh to work for Linux, or c:/cygwin/bash.exe to work
on Windows using Cygwin, but can't support both.

It would be nice if the shell setting can be a slave configuration so we can
configure the Windows machines to use c:/cygwin/bash.exe for a shell and Linux
machines to use /bin/sh.

That way we can use shell commands for everything and don't have to use the
horrible Windows batch commands.