Fix OptimizationLevel mapping for Os

[yashssh]

For Os LLVM defined speed level is 2 not 1.
(https://github.com/llvm/llvm-project/blob/main/llvm/lib/Passes/OptimizationLevel.cpp)

fixes #1306

[yashssh]

Not sure what the macOS failure is about

[stuartarchibald]

Not sure what the macOS failure is about

I've restarted it, it may have been network related and a download was interrupted but a process returned 0 and so continued to the next step in the CI build.

[stuartarchibald]

Thanks for the patch. From inspection, I think this now matches the LLVM logic.

[dnadlinger]

As mentioned in #1306, I wonder about the backwards compatibility angle here, though – as an llvmlite user, there now isn't a piece of code I can write to access Os that works with both 0.44 as well as the next release.

[yashssh]

While I agree there isn't a piece of code that will work with both 0.44 and the next release for Os. I think adding backward compatibility for this might not be ideal.

(Edit: Deleted a part of the comment, got confused in the release timeline)