[llvm] [mlir:bazel] Fix build broken by #169670. (PR #169804)

[Ingo Müller via llvm-commits]

ingomueller-net wrote:

I am pretty sure that the PR fixes a previous issue and doesn't introduce a new one. In particular, the CI failures are due to some external problem and probably transient. Will merge now. Please revert if this causes problems.

https://github.com/llvm/llvm-project/pull/169804