Rollup merge of #120890 - TimNN:relax-patches-check, r=onur-ozkan

Adapt `llvm-has-rust-patches` validation to take `llvm-config` into account.

This adapts an assertion that was added in #119556.

The current assertion does not take the `llvm-config` setting into accounts, which does not match the `llvm-has-rust-patches` documentation, which states:

> This would be used in conjunction with either an llvm-config or build.submodules = false.

(It also breaks my workflow: I build LLVM separately, but do have the rust patches applied).

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**edit:** Originally this PR just removed the assertion, but it now implements the alternative mentioned here:

An alternative fix would be to take `llvm-config` into account in the assertion, but to me the assertion seems to provide little value, thus the simpler fix of just removing it.

cc `@onur-ozkan,` in case I'm missing a reason to keep the assertion.

Author: matthiaskrgr