[OpenMP] Remove compilation warning when using clang to compile bc files.

Summary: Minor printf format correction. NVCC ignore those. Clang will give warning on these if debug is enabled.

Reviewers: grokos

Reviewed By: grokos

Subscribers: openmp-commits

Tags: #openmp

Differential Revision: https://reviews.llvm.org/D45528

llvm-svn: 330944