Using -D cppflags possible?

Hello all,

great tool firstly!
Is there a way to use or config new cppflags like -DTESTDEFINE for example?

I would like to enable those macros from CLI for a variant handling.

_Example:_
```c
// Get right parameter based on variant
#if defined(TESTDEFINE)
par = TEST_PAR;
#else 
par = DEFAULT_PAR;
#endif
```

Hope someone can assist me.

Thanks!

