[llvm] [mlir] Fix LLVM_ENABLE_ABI_BREAKING_CHECKS macro check: use #if instead of #ifdef (PR #110185)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

Yes this is a valid combination, I just don't understand why anyone would want it in practice. It's been a while, but from memory I see the ABI_BREAKING_CHECKS as checks that are extras on top of the assertions.

https://github.com/llvm/llvm-project/pull/110185