Inline debug variable.

Summary:
In a release build this variable becomes unused and may break the build
with `-Werror,-Wunused-variable`.

Reviewers: gribozavr2, jdoerfert, sstefan1

Reviewed By: gribozavr2

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73683