MC: Change the streamer ctors to take an object writer instead of a stream. NFCI.

The idea is that a client that wants split dwarf would create a
specific kind of object writer that creates two files, and use it to
create the streamer.

Part of PR37466.

Differential Revision: https://reviews.llvm.org/D47050

llvm-svn: 332749
diff --git a/clang/tools/driver/cc1as_main.cpp b/clang/tools/driver/cc1as_main.cpp
index bd67819..6058852 100644
--- a/clang/tools/driver/cc1as_main.cpp
+++ b/clang/tools/driver/cc1as_main.cpp
@@ -29,6 +29,7 @@
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCParser/MCAsmParser.h"
 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/MC/MCRegisterInfo.h"
@@ -426,11 +427,12 @@
     MCTargetOptions MCOptions;
     std::unique_ptr<MCAsmBackend> MAB(
         TheTarget->createMCAsmBackend(*STI, *MRI, MCOptions));
+    std::unique_ptr<MCObjectWriter> OW = MAB->createObjectWriter(*Out);
 
     Triple T(Opts.Triple);
     Str.reset(TheTarget->createMCObjectStreamer(
-        T, Ctx, std::move(MAB), *Out, std::move(CE), *STI, Opts.RelaxAll,
-        Opts.IncrementalLinkerCompatible,
+        T, Ctx, std::move(MAB), std::move(OW), std::move(CE), *STI,
+        Opts.RelaxAll, Opts.IncrementalLinkerCompatible,
         /*DWARFMustBeAtTheEnd*/ true));
     Str.get()->InitSections(Opts.NoExecStack);
   }