[llvm] [PGO] Add missing target datalayout in test (PR #169520)

[Joel E. Denny via llvm-commits]

jdenny-ornl wrote:

Thanks.  I'll try that.  There are other loop-vectorize tests (pr30806.ll pr35743.ll pr38697.ll) in the same directory that target x86_64 and do not have such a REQUIRES line, but perhaps the transformation somehow doesn't require the backend in their cases.

https://github.com/llvm/llvm-project/pull/169520