[clang] [flang] [mlir] [flang] Add support for -mprefer-vector-width=<value> (PR #141380)

[Tarun Prabhu via cfe-commits]

https://github.com/tarunprabhu approved this pull request.

Thanks for the all the changes. LGTM.

https://github.com/llvm/llvm-project/pull/141380