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

[Cameron McInally via cfe-commits]

mcinally wrote:

@tarunprabhu Would you mind mashing the "Merge" button? It looks like getting commit access approval is taking longer than expected.

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