ELF: Inline function LazyObjFile::getBuffer() into caller. NFCI.

[pcc]

Summary

It's a little confusing for a function named getSomething() to be
mutating anything. Inlining this function should make it a little
clearer what's going on.

lld/ELF/InputFiles.h

LazyObjFile(MemoryBufferRef M, StringRef ArchiveName,
               uint64_t OffsetInArchive)
       : InputFile(LazyObjKind, M), OffsetInArchive(OffsetInArchive) {
     this->ArchiveName = ArchiveName;
   }
 
   static bool classof(const InputFile *F) { return F->kind() == LazyObjKind; }
 
   template <class ELFT> void parse();
-  MemoryBufferRef getBuffer();
   InputFile *fetch();
   bool AddedToLink = false;
 
 private:
   template <class ELFT> void addElfSymbols();
 
   uint64_t OffsetInArchive;
 };

lld/ELF/InputFiles.cpp

case ELF64LEKind:
     return make<SharedFile<ELF64LE>>(MB, DefaultSoName);
   case ELF64BEKind:
     return make<SharedFile<ELF64BE>>(MB, DefaultSoName);
   default:
     llvm_unreachable("getELFKind");
   }
 }
 
-MemoryBufferRef LazyObjFile::getBuffer() {
-  if (AddedToLink)
-    return MemoryBufferRef();
-  AddedToLink = true;
-  return MB;
-}
-
 InputFile *LazyObjFile::fetch() {
-  MemoryBufferRef MBRef = getBuffer();
-  if (MBRef.getBuffer().empty())
+  if (AddedToLink)
     return nullptr;
+  AddedToLink = true;
 
-  InputFile *File = createObjectFile(MBRef, ArchiveName, OffsetInArchive);
+  InputFile *File = createObjectFile(MB, ArchiveName, OffsetInArchive);
   File->GroupId = GroupId;
   return File;
 }
 
 template <class ELFT> void LazyObjFile::parse() {
   // A lazy object file wraps either a bitcode file or an ELF file.
   if (isBitcode(this->MB)) {
     std::unique_ptr<lto::InputFile> Obj =