Many thanks for all the suggestions. Since NEEDEDFLAG can also be set by: nim c -d:NEEDEDFLAG etc.etc. Run
I need to use defined(NEEDEDFLAG) instead of declared(NEEDEDFLAG). However the following inside nim.cfg worked for me: @if BGMAP: define:BGDUMP @end Run which is the actual example in use. Where (URL) are the @ commands for nim.cfg documented?? I could not find them in [https://nim-lang.org/docs/nimc.html](https://nim-lang.org/docs/nimc.html)