Moreover, you cannot say compilers are deterministic. There are situations where they are not (at least for the user).

https://krystalgamer.github.io/high-level-game-patches/

I'm not following. Which part of this is nondeterministic?

The language being complicated to write and the compiler being confusing to use isn't an indicator of determinism. If GCC were truly nondeterministic, that'd be a pretty major bug.

Also, note that I mentioned that the output behavior is deterministic. I'm not referring to reproducible builds, just that it always produces code that does what the source specifies (in this case according to a spec).