[inputGraph] Associate Resolve state with appropriate nodes

This associates resolveState to FileNodes. The control node derive
their resolution state from the inputElements that are contained in
it.

This makes --start-group/--end-group to work with ELF linking.

llvm-svn: 192269
diff --git a/lld/lib/Core/Resolver.cpp b/lld/lib/Core/Resolver.cpp
index ca383ab..c8d1549 100644
--- a/lld/lib/Core/Resolver.cpp
+++ b/lld/lib/Core/Resolver.cpp
@@ -292,6 +292,7 @@
   ScopedTask task(getDefaultDomain(), "resolveUndefines");
 
   while (ErrorOr<File &> nextFile = _context.nextFile()) {
+    _context.setResolverState(Resolver::StateNoChange);
     if (error_code(nextFile) == InputGraphError::no_more_files)
       break;
     if (nextFile->kind() == File::kindObject)