[clang] [llvm] [KeyInstr] Add DISubprogram::keyInstructions bit (PR #144107)

[Jeremy Morse via cfe-commits]

https://github.com/jmorse approved this pull request.

No strong opinion on the arguments really, thing can always be re-rationalised in the future.

> Not sure I follow this question - can you elaborate?

It's a draft fragment of one of the questions I asked that floated to the bottom, whoops.

https://github.com/llvm/llvm-project/pull/144107