I don't know if you have a specific reason for building unixODBC, because you could save yourself the trouble:
RPM search resultThis rpm places the configuration file in /etc.
Since "${prefix}/etc" does not seem to be repeated, I would think that's the only thing you would have to change.
Imho, SME seems to stick with rpm's as much as possible, and create e-smith- (smeserver-) rpm's whenever needed/desired, containing for example templates for configuration.
There should be enough information documented on contribs to get you started if you wish to conform to sme guidelines.
After that the next step would be the dev mailing list..