message: Replace forward decl with include to unbreak the build.
diff: #include "llvm/ADT/StringMap.h" // for StringMap
  #include "llvm/ADT/StringRef.h" // for StringRef, StringLiteral
  #include "llvm/Support/FormatVariadic.h"
  +#include "llvm/Support/ManagedStatic.h"
  #include "llvm/Support/RWMutex.h"
  #include <atomic>
  namespace llvm {
  class raw_ostream;
  }
  -namespace llvm {
  -template <class C> class ManagedStatic;
  -}
  //----------------------------------------------------------------------
  // Logging Options
  //----------------------------------------------------------------------
  