[llvm] [FuncSpec] Invalidate analysis by setting MadeChanges explicitly (PR #155833)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

> > Why not set `MadeChanges` here https://github.com/llvm/llvm-project/blob/main/llvm/lib/Transforms/IPO/SCCP.cpp#L174 and leave everything else as is?
> 
> I prefer the current form just for direct logic, and for other similar changes in funcspec in future. I can set it as you suggest if you insist, thanks.

I'd also rather keep the destructor, if possible.

https://github.com/llvm/llvm-project/pull/155833