In my particular CMake project, I have three CPP files:

```
a.cpp
b.cpp
c.cpp

```

I want 'a.cpp' to be compiled in all configurations (release & debug).  

I only want 'b.cpp' to be compiled in DEBUG configuration.  

I only want 'c.cpp' to be compiled in RELEASE configuration.

How can I do this? I need something similar to the `debug` and `optimized` keywords that are accepted by the `target_link_libraries()` CMake operation.