Disable ROCM when building mobile libtorch. (#34478)
Summary:
When a system has ROCm dev tools installed, `scripts/build_mobile.sh` tried to use it.
This PR fixes looking up unused ROCm library when building libtorch mobile.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34478
Differential Revision: D20388147
Pulled By: ljk53
fbshipit-source-id: b512c38fa2d3cda9ac20fe47bcd67ad87c848857
