PassWrapper: handle move of OptimizationLevel class out of PassBuilder
PassWrapper: handle move of OptimizationLevel class out of PassBuilder

This is the first build break of the LLVM 14 cycle, and was caused by
https://reviews.llvm.org/D107025. Mercifully an easy fix.

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust