IRGen: dont use autolink-extract for COFF targets

COFF supports the `.drectve` section for embedding linker directives.  LLVM has
long supported emitting this section.  With this move, ELF shall become the only
target needing the autolink-extract functionality.

lib/IRGen/IRGenModule.cpp

@@ -879,6 +879,7 @@ void IRGenModule::emitAutolinkInfo() {
   switch (TargetInfo.OutputObjectFormat) {
   case llvm::Triple::UnknownObjectFormat:
     llvm_unreachable("unknown object format");
+  case llvm::Triple::COFF:
   case llvm::Triple::MachO: {
     llvm::LLVMContext &ctx = Module.getContext();
 
@@ -897,7 +898,6 @@ void IRGenModule::emitAutolinkInfo() {
     }
     break;
   }
-  case llvm::Triple::COFF:
   case llvm::Triple::ELF: {
     // Merge the entries into null-separated string.
     llvm::SmallString<64> EntriesString;