Do you like have any idea what you're talking about? Or are you just making it up for internet points? The target is part of the input.

Lemme ELI5

https://github.com/llvm/llvm-project/tree/main/llvm/test/Cod...

You see how this folder has folders for each target? Then within each target folder there are tests (thousands of tests)? Each of those tests is verified deterministically on each commit.

Edit: there's an even more practical way to understand how you're wrong: if what you were saying were true, ccache wouldn't work.