[DebugInfo] - Attemp to fix BB after r310915.

Not sure what BB does not like.

While building module 'LLVM_DebugInfo_DWARF' imported from /home/buildbot/modules-slave-2/clang-x86_64-linux-selfhost-modules-2/llvm.src/lib/DebugInfo/DWARF/DWARFAbbreviationDeclaration.cpp:10:
In file included from <module-includes>:7:
In file included from /home/buildbot/modules-slave-2/clang-x86_64-linux-selfhost-modules-2/llvm.src/include/llvm/DebugInfo/DWARF/DWARFContext.h:29:
/home/buildbot/modules-slave-2/clang-x86_64-linux-selfhost-modules-2/llvm.src/include/llvm/DebugInfo/DWARF/DWARFObject.h:30:17: error: declaration of 'object' must be imported from module 'LLVM_Object.Decompressor' before it is required
  virtual const object::ObjectFile *getFile() const { return nullptr; }
                ^
/home/buildbot/modules-slave-2/clang-x86_64-linux-selfhost-modules-2/llvm.src/include/llvm/Object/Decompressor.h:18:11: note: previous declaration is here
namespace object {

http://lab.llvm.org:8011/builders/clang-x86_64-linux-selfhost-modules-2/builds/10766

llvm-svn: 310918