[llvm] [X86] Don't always separate conditions in `(br (and/or cond0, cond1))` into separate branches (PR #81689)

[via llvm-commits]

goldsteinn wrote:

@nikic
NOTE: going to push this, it will increase instruction count on stage2 compile time benchmarks (saves branch misses).

https://github.com/llvm/llvm-project/pull/81689