Support older versions of LLVM

[vaivaswatha]

No description provided.

[vaivaswatha]

@adriaanjacobs can you confirm that this branch works for you? I'll merge it after that.

[adriaanjacobs]

Just tested; it doesn't work on LLVM 15 because of the explicit version checks for at least LLVM 16. Would you like to drop support for 15 entirely, or would you be open to keeping it? I would be happy to contribute a patch that keeps support for 15 through 23.

I'm emphasizing LLVM 15 because it was the last version with non-opaque pointer support (albeit deprecated already).

[vaivaswatha]

Just tested; it doesn't work on LLVM 15 because of the explicit version checks for at least LLVM 16. Would you like to drop support for 15 entirely, or would you be open to keeping it? I would be happy to contribute a patch that keeps support for 15 through 23.

I'm emphasizing LLVM 15 because it was the last version with non-opaque pointer support (albeit deprecated already).

Can you check now? A full review of the PR would be helpful too. The CI changes that I added are mostly AI generated (especially the python test scripts). They seem to be working, but if you understand it well enough and have comments, do let me know.