1.6 tests are failing

[simonbyrne]

https://github.com/JuliaLang/PackageCompiler.jl/runs/7175755312?check_suite_focus=true#step:4:340

InitError(mod=:LLVMExtra_jll, error=ErrorException("Cannot locate artifact 'LLVMExtra' in '/tmp/jl_s8rPQE/packages/LLVMExtra_jll/RuRRc/Artifacts.toml'"))

[KristofferC]

Yeah, I merged a test that failed on 1.6 at a time when we didn't have 1.6 CI. It is a bit tricky to make this conditional on the julia version though.

[DilumAluthge]

Should be fixed by #771