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

[Matt Arsenault via cfe-commits]

arsenm wrote:

> Just to clarify, the motivating issue is not performance. A [Gromacs](https://github.com/ROCm/Gromacs) test case fails due to incorrect results (floating point result exceeds some tolerance).

Which is a completely different issue and this is not a correctness fix 

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