How can a source file be tagged to always build, irrespective of whether it's (apparently) changed or not?

Keil has a specific check-box to do this - is there an equivalent in RIDE?

eg, I find it really useful to have a build timestamp in the executable - so that you can be sure you're working with the right revision.
This is most easily achieved by having a file use the __DATE__ and __TIME__ macros, and ensure that it is always recompiled on every build.

Another way to do it would be via an external command that runs before the main build starts:
http://www.raisonance.com/Forum/punbb/viewtopic.php?pid=8708#p8708