[llvm] [GOFF] Introduce GOFFWriter class (PR #131216)

[Fangrui Song via llvm-commits]

================
@@ -295,6 +284,35 @@ uint64_t GOFFObjectWriter::writeObject(MCAssembler &Asm) {
   return OS.getWrittenSize();
 }
 
+namespace {
+
+class GOFFObjectWriter : public MCObjectWriter {
----------------
MaskRay wrote:

If you will change AsmPrinter or a targetstreamer to be aware of GOFF-specifics, it would be better to expose the class to a header.

In 70c52b62c5669993e341664a63bfbe5245e32884 , I exported ELF and enabled a lot of simplification to MCAssembler/MCELFStreamer.

https://github.com/llvm/llvm-project/pull/131216