search for: deletefunctionaftercodegen

Hi all After codegen for a given function, the IR should no longer be needed. In the AsmPrinter we convert from MI->MCInstr, and then we never go back and look at the IR during the MC layer. I’ve prototyped a simple pass which can be (optionally) scheduled to do just this. It is added at the end of addPassesToEmitFile. It is optional so that clang can continue to leak the IR with