If you have a compiler the same source code and the same options, it should generate the same output everything provided you aren't using some compiler pragmas or something similar that embeds timestamps or random numbers or similar. If you give an LLM the same input, it can generate different outputs (controlled by the temperature setting).
I'll be charitable here but you need to go out of your way to introduce non-determinism. Bit reproducible builds and distros exist so it is possible to have an entire distro that can be reliably reproduced bit-by-bit on different systems and at different times.
It's the other direction. You have to put in an extreme amount of effort, like Debian has, which you can just piggyback off of, to cause determinism to be introduced. 2013 they started that initiative. They're reasonably there, thirteen years later, but to disregard the amount of effort it took to get there would be to forget history. Give ChatGPT thirteen more years to iterate, and see where it is then.
Folks who bring up these "gotchas" should be forbidden from using or taking advantage of the things they are disingenuously whataboutism-ing. Reminds me of sovereign citizen behavior.