No, in that case you would #include all your .c files in one .c file and compile that for release, but would otherwise work in the usual manner. CMake actually has builtin support for doing just that.

That would be a nicer way to do it, but it doesn't contradict what I said.

Any halfway decent developer that wants single file optimization but doesn't want to author the source code in one file will do this.

See "Unity build".

I talked to the developer, and it was him who mentioned this, and he was not proud of that part ;).