> But then I tried to run it on a build server I was using (Netlify), and I got this extremely strange error message: “File not found”. I straced it, and sure enough execve was returning the error code ENOENT, which means “File not found”. This was kind of maddening because the file was DEFINITELY there and it had the correct permissions and everything.

This is an infuriating property of the runtime linkers on both Linux and Windows: if you're trying to load file A, and dependency B of file A does not exist, you just get "file not found" with no indication of which file it was, and it's extremely hard to debug. At least on linux the "show dependencies" tool is built in.