[clang] [lld] [lld][LTO] Respect `-fno-slp-vectorize` for the LTO pipeline (PR #201585)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> Can this info be added to the IR e.g. a module flag or the like? Ideally we don't have to specially recognize every opt flag in the linker

The pass pipeline isn't really part of the program semantics, I don't think it belongs in the IR 

https://github.com/llvm/llvm-project/pull/201585