on MacOS, Nim libraries (e.g.: bignum) don't link properly.  My only experience
with Nim is via Rosetta Code.  My Nim and Nimble come from MacPorts. The bignum
library seems to build ok; building the Nim code that requires that library
seems to build ok; but when trying to execute I get "could not load:
libgmp.dylib".  On the Rosetta Code website, in the Nim Category Talk page, I
show more details.  It seems that on MacOS the Nim library must be written in
Nim for it to be linked properly.  I have a Mac with the M1 chip.  In an email
thread with MacPorts, it was noted that this failure occurs with the Intel-based
MacOS as well.  They feel strongly that it is not a MacPorts failure and even
have some ideas to assist in the correct linkage process if Nim people are
interested.