change to use clang if NDK >= 18 (#18914)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18914
ghimport-source-id: 4d9d9322ee5559d96e13533ec37ff3be86a0227c
Reviewed By: ezyang
Differential Revision: D14794162
Pulled By: ljk53
fbshipit-source-id: caac55e12b1e62bf6ebcc6e2062d5ed122ad4e64
