Fix ObjCPass on big-endian host

[tstellar]

Summary

This fixes test/mach-o/objc-image-info-pass-output.yaml on
big-endian hosts.

[ruiu]

LGTM

lib/ReaderWriter/MachO/ObjCPass.cpp

59–60

Is there any reason not to write

normalized::write32(...)

?

lib/ReaderWriter/MachO/ObjCPass.cpp

 //===- lib/ReaderWriter/MachO/ObjCPass.cpp -------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 //===----------------------------------------------------------------------===//
 
 #include "ArchHandler.h"
 #include "File.h"
+#include "MachONormalizedFileBinaryUtils.h"
 #include "MachOPasses.h"
 #include "lld/Core/DefinedAtom.h"
 #include "lld/Core/File.h"
 #include "lld/Core/LLVM.h"
 #include "lld/Core/Reference.h"
 #include "lld/Core/Simple.h"
 #include "lld/ReaderWriter/MachOLinkingContext.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 
 namespace lld {
 namespace mach_o {
 
 ///
 /// ObjC Image Info Atom created by the ObjC pass.
 ///
 class ObjCImageInfoAtom : public SimpleDefinedAtom {
 public:
-  ObjCImageInfoAtom(const File &file,
+  ObjCImageInfoAtom(const File &file, bool isBig,
                     MachOLinkingContext::ObjCConstraint objCConstraint,
                     uint32_t swiftVersion)
       : SimpleDefinedAtom(file) {
 
     Data.info.version = 0;
 
     switch (objCConstraint) {
     case MachOLinkingContext::objc_unknown:
       llvm_unreachable("Shouldn't run the objc pass without a constraint");
     case MachOLinkingContext::objc_supports_gc:
     case MachOLinkingContext::objc_gc_only:
       llvm_unreachable("GC is not supported");
     case MachOLinkingContext::objc_retainReleaseForSimulator:
       // The retain/release for simulator flag is already the correct
       // encoded value for the data so just set it here.
       Data.info.flags = (uint32_t)objCConstraint;
       break;
     case MachOLinkingContext::objc_retainRelease:
       // We don't need to encode this flag, so just leave the flags as 0.
       Data.info.flags = 0;
       break;
     }
 
     Data.info.flags |= (swiftVersion << 8);
+
+    using normalized::write32;
+    write32(Data.bytes + 4, Data.info.flags, isBig);
   }
 
   ~ObjCImageInfoAtom() override = default;
 
   ContentType contentType() const override {
     return DefinedAtom::typeObjCImageInfo;
   }
 
llvm::Error perform(SimpleFile &mergedFile) override {
     mergedFile.addAtom(*getImageInfo());
 
     return llvm::Error::success();
   }
 
 private:
 
   const DefinedAtom* getImageInfo() {
-    return new (_file.allocator()) ObjCImageInfoAtom(_file,
+    bool IsBig = MachOLinkingContext::isBigEndian(_ctx.arch());
+    return new (_file.allocator()) ObjCImageInfoAtom(_file, IsBig,
                                                      _ctx.objcConstraint(),
                                                      _ctx.swiftVersion());
   }
 
   const MachOLinkingContext   &_ctx;
   MachOFile                   &_file;
 };
 
 
 
 void addObjCPass(PassManager &pm, const MachOLinkingContext &ctx) {
   pm.add(llvm::make_unique<ObjCPass>(ctx));
 }
 
 } // end namespace mach_o
 } // end namespace lld