Hi,
Alternatively, you can link separate object file (.o) as an other object file (e.g. place the affected object files into a custom folder e.g. <Project home folder>\obj\) :

I'd also suggest you to disable debug information generation specifically for these source files. This will make them even harder to understand since symbol information is extracted from the compiled object file.
To do so just right click on specific source file and go to properties (main.c in the example):

Once the change is confirmed the file decorator appears (little black pin) indicating that the source file has a different to default build options :

Hope it helps.
Stan