Comply llama2 runner with gcc 11.4 (#3140)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3140

This seems like a simple change so that it can compile with gcc 11.4

bypass-github-export-checks
bypass-github-pytorch-ci-checks
bypass-github-executorch-ci-checks

Reviewed By: digantdesai

Differential Revision: D56320381

fbshipit-source-id: 577a60bac78ed01ad450fcb58dbccc7f04fd5067