quick changes that don't require a full recompilation generally mean intermediate files are lying around, which means you only need to recompile changed files and relink. this is usually pretty fast until you start changing headers or something like that. (I'm very used to projects with 30 minute plus full compile times taking less than 10 seconds to recompile and relink single-file changes.)

this is not to say that gdb won't save hilarious amounts of time or that you can be a good C coder without understanding a debugger (I don't think you can), just that the huge compile time thing isn't true most of the time.