[libunwind] Silence warnings about unused variables. NFC.

This variable was considered unused when NDEBUG was defined.

Differential Revision: https://reviews.llvm.org/D124911

NOKEYCHECK=True
GitOrigin-RevId: 6123e9c0d03bf1e3f43c3851f4122a7267b33c28
1 file changed
tree: 8b157b9ca08c1575122e5d441ac3cee346a75ba9
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT