[llvm] [CFGPrinter] Allow CFG dumps with a given filename (PR #112906)

[Lewis Crawford via llvm-commits]

LewisCrawford wrote:

Requesting review from @WenleiHe and @david-xl , as they reviewed a similar CFGPrinter debugger utils patch a few years ago in https://reviews.llvm.org/D77978

https://github.com/llvm/llvm-project/pull/112906