Sorry, Trev, I'm not very experienced in such operations; in fact I did it the first time.
I did not change the path after having edited NSString.inc. That was it.
Being back to /usr/local/share/fpcsrc/3.2.0 everything was running perfectly.
Thank you very much for your help. Now I have a workaround for fpc 3.2.0 for MacOS, it's OK for me. Nevertheless I will open a bug report.