[llvm] [XRay][X86] Fix stack alignment for custom event calls. (PR #89360)

[Ricky Zhou via llvm-commits]

rickyz wrote:

> Thanks! This is similar to EmitLoweredTLSAddr

Yeah, I copied the approach taken there - I kept them separate mostly because I couldn't think of a great name capturing a nice conceptual overlap ("emit thing that will turn into a function call, either at compile time or in the case of xray, conditionally at runtime") - I guess I can also imagine the two diverging in the future - but lmk if you prefer otherwise!

https://github.com/llvm/llvm-project/pull/89360