Change Between Gnu Make and Clearmake Compilers During a Build

Note, neither GNU make nor clearmake are compilers.

All make versions are just tools for running other commands, so you can just write a rule that will run a different make as a command:

run-make:
        gmake do-something

Now when the run-make rule is invoked it will call GNU make (here called gmake, but it might be called make or whatever) to build a target do-something. Once that's done it'll return back to the current make version (presumably clearmake).

With the minimal information you provided, that's the best we can do.