[llvm] [FileCheck] Limit quadratic partial-match search behavior (PR #147833)

[via llvm-commits]

dyung wrote:

> Should be fixed in [ce9d515](https://github.com/llvm/llvm-project/commit/ce9d515813f8e1fe8578a3f889abe5325250309e)

Looks like this did not work. :(

https://lab.llvm.org/buildbot/#/builders/144/builds/31023

https://github.com/llvm/llvm-project/pull/147833