Adding "-C <dir>" option to runtest(1)

I would like to add an option to runtest for changing directory very 
early (actually in the shell launcher; Tcl would ignore it) as part of 
fixing the current Automake misintegration.  This option would be 
analogous to the "-C" option to GNU make.  Unfortunately, GNU make uses 
"--directory" as the corresponding long option and that is already used 
for a different purpose in DejaGnu.

This is a problem because the recursive runtest runs in the DejaGnu 
testsuite need to use a different site.exp from the outer runtest.

I have a few options:

(1)  Use a different long option name, perhaps "--base-directory".
(2)  Add a shell script shim for the testsuite to use that changes 
directory and invokes "runtest".
(3)  Allow overriding the configfile name (default "site.exp") via 
command-line option.

I prefer option (1), since the functionality is strongly analogous to 
GNU make:  both programs examine hard-coded files relative to the 
directory in which they start.

-- Jacob