[llvm] [PowerPC][AIX] Emit PowerPC version for XCOFF (PR #95510)

[Chen Zheng via llvm-commits]

================
@@ -1171,6 +1171,7 @@ void MCStreamer::emitFileDirective(StringRef Filename,
                                    StringRef CompilerVersion,
                                    StringRef TimeStamp, StringRef Description) {
 }
+void MCStreamer::emitMachineDirective(StringRef CPU) {}
----------------
chenzheng1030 wrote:

nit: maybe we can also add `llvm_unreachable` like below line 1176

https://github.com/llvm/llvm-project/pull/95510