Extract an utility for computing symbol sizes on MachO and COFF.

I will add a second user in the next commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240366 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Object/SymbolSize.h

@@ -0,0 +1,26 @@
+//===- SymbolSize.h ---------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Declares the writeArchive function for writing an archive file.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECT_SYMBOLSIZE_H
+#define LLVM_OBJECT_SYMBOLSIZE_H
+
+#include "llvm/Object/ObjectFile.h"
+
+namespace llvm {
+namespace object {
+ErrorOr<std::vector<std::pair<SymbolRef, uint64_t>>>
+computeSymbolSizes(const ObjectFile &O);
+}
+} // namespace llvm
+
+#endif