Rust tests failing with LLVM version mismatch regarding opaque pointers

[kquick]

yapall> error: Opaque pointers are only supported in -opaque-pointers mode (Producer: 'LLVM15.0.7' Reader: 'LLVM 14.0.6')
yapall> error: test failed, to rerun pass `--test pointer`

(See https://github.com/GaloisInc/yapall/actions/runs/6029699696/job/16359835202?pr=47#step:5:950 or https://github.com/GaloisInc/yapall/actions/runs/6030069826/job/16361088971?pr=50)

This is a specific instance of the general issues noted by #46

[langston-barrett]

Looks like this is specifically the tests that perform pointer analysis on the output of rustc. I think what happened here is that when I started developing yapall, rustc was based on LLVM 14, but these days it's based on LLVM 15.