English isn't my first language, so when I read "reproducible" I thought "deterministic"; I also didn't think you'd be working on the "vendoring" problem since I thought it was a solved issue (which it isn't for all the reasons in the post). Anyways, thanks for your work.

I think the compilers that produce elf output are almost deterministic, at least when producing a fully static binary (no CGO).

I don't think that holds for mach-o or PE binaries, but I'm really speaking off the cuff here, as I said, others care about this and are working on it separately.

However, English is my first language, and I thought exactly the same.

Does JIT (or late/deploy time optimize/link) help here? Would it be easier to make deterministic builds when optimizer is not involved?

Nope, this is about the source that goes into the compiler.