Partially revert r308329 to fix MSVC

This is an attempt to fix an upstream bug at
https://bugs.llvm.org/show_bug.cgi?id=36096 by applying the local solution found
there and otherwise reverting the behavior that seems to be causing problems for
us. I'm not actually sure what's going on here, but hopefully it's not too bad
for us...

Author: alexcrichton

lib/Object/ArchiveWriter.cpp

@@ -305,8 +305,7 @@ static bool isArchiveSymbol(const object::BasicSymbolRef &S) {
     return false;
   if (!(Symflags & object::SymbolRef::SF_Global))
     return false;
-  if (Symflags & object::SymbolRef::SF_Undefined &&
-      !(Symflags & object::SymbolRef::SF_Indirect))
+  if (Symflags & object::SymbolRef::SF_Undefined)
     return false;
   return true;
 }