[CodeView] Raise the source to ID map out of the TypeStreamMerger.

This map will be needed to rewrite symbol streams after re-writing
the corresponding type streams.

llvm-svn: 303390
diff --git a/lld/COFF/PDB.cpp b/lld/COFF/PDB.cpp
index 4bbf9c7..0266148 100644
--- a/lld/COFF/PDB.cpp
+++ b/lld/COFF/PDB.cpp
@@ -108,6 +108,7 @@
     BinaryByteStream Stream(Data, support::little);
     codeview::CVTypeArray Types;
     BinaryStreamReader Reader(Stream);
+    SmallVector<TypeIndex, 128> SourceToDest;
     // Follow type servers.  If the same type server is encountered more than
     // once for this instance of `PDBTypeServerHandler` (for example if many
     // object files reference the same TypeServer), the types from the
@@ -116,8 +117,8 @@
     Handler.addSearchPath(llvm::sys::path::parent_path(File->getName()));
     if (auto EC = Reader.readArray(Types, Reader.getLength()))
       fatal(EC, "Reader::readArray failed");
-    if (auto Err =
-            codeview::mergeTypeStreams(IDTable, TypeTable, &Handler, Types))
+    if (auto Err = codeview::mergeTypeStreams(IDTable, TypeTable, SourceToDest,
+                                              &Handler, Types))
       fatal(Err, "codeview::mergeTypeStreams failed");
   }