I was more talking about the need to implement this layer yourself, when it should be taken care of by the build system (though I don't know of any build system

I was more talking about the need to implement this layer yourself, when it should be taken care of by the build system (though I don't know of any build systems that can easily implement your suggestion, since it has to somehow redirect the output of a code-generation step to another file). Agreed that there are performance differences, though in my experience hashing is quite acceptable even for large projects if used reasonably (only hashing inputs to build steps if they are also outputs of another build step).