Ha, your comment was my first introduction to Nim but it looks interesting so I "brew install nim" and tried your test (thanks!) with "nim c test.nim && ./test" on macOS and my results is the opposite of your: hello1 is garbled while hello2 works.

I bit of googling found the next steps "nimble install minx" but for compiling your win.nim example I had to use "nim --noMain --threads:on c -r win.nim" but the result worked. However AFAIK, there's no official way to make statically linked binaries on the latest macOS.