[clang] nolock/noalloc attributes (PR #84983)

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Sirraide wrote:

> * Conversions between functions / function pointers with and without the attribute work in C++ but not in C and I'm a bit lost (there's a bunch of debug logging around this e.g. Sema::IsFunctionConversion and Sema::ImpCastExprToType)

Er, I’ll see if I can find some time to take a look at this, but I’m not sure what the problem is off the top of my head.

https://github.com/llvm/llvm-project/pull/84983