Just out of curiosity, can you try giving rwx permissions for the local user to the src folder where you have compiled Bro, and see if that works?
Usually, the debug.log isn’t logged into the spool and log dirs.
Another thing you could try is, try running Bro as root again and once it succeeds, use “locate debug.log” command to check to see where exactly it is getting generated and then try giving that folder the rwx permissions for the local user you would want to run Bro as.
-Fatema.