[lld] [lld][COFF][LTO] Implement /lldemit:asm option (PR #67079)

[Alexandre Ganea via llvm-commits]

================
@@ -87,13 +87,21 @@ lto::Config BitcodeCompiler::createConfig() {
   c.RunCSIRInstr = ctx.config.ltoCSProfileGenerate;
   c.PGOWarnMismatch = ctx.config.ltoPGOWarnMismatch;
 
-  if (ctx.config.emit == EmitKind::LLVM) {
+  switch (ctx.config.emit) {
+  case EmitKind::Obj:
----------------
aganea wrote:

Sorry actually I meant to suggest:
```
if (ctx.config.emit == EmitKind::LLVM) {
.. 
} else if (ctx.config.emit == EmitKind::ASM) {
..
}
```
I find the switch-case is less suitable here. Forget my comment about unreachable, a potential new `EmitKind`
 enumeration might add code in other places in this function, or not all, like `EmitKind::Obj`.

https://github.com/llvm/llvm-project/pull/67079