[VPlan] Replace LLVM_ATTRIBUTE_USED with ifndef NDEBUG

Minor replacement. LLVM_ATTRIBUTE_USED was introduced to silence
a warning but using #ifndef NDEBUG makes more sense in this case.

Reviewers: dblaikie, fhahn, hsaito

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D47498


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333476 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed