[LinkingContext] make LinkingContext non-const

llvm-svn: 192183
diff --git a/lld/lib/ReaderWriter/CoreLinkingContext.cpp b/lld/lib/ReaderWriter/CoreLinkingContext.cpp
index bc9a009..db17d57 100644
--- a/lld/lib/ReaderWriter/CoreLinkingContext.cpp
+++ b/lld/lib/ReaderWriter/CoreLinkingContext.cpp
@@ -271,8 +271,9 @@
 
 CoreLinkingContext::CoreLinkingContext() {}
 
-bool CoreLinkingContext::validateImpl(raw_ostream &diagnostics) {
+bool CoreLinkingContext::validateImpl(raw_ostream &) {
   _reader = createReaderYAML(*this);
+  _writer = createWriterYAML(*this);
   return true;
 }
 
@@ -289,11 +290,7 @@
   }
 }
 
-Writer &CoreLinkingContext::writer() const {
-  if (!_writer)
-    _writer = createWriterYAML(*this);
-  return *_writer;
-}
+Writer &CoreLinkingContext::writer() const { return *_writer; }
 
 ErrorOr<Reference::Kind>
 CoreLinkingContext::relocKindFromString(StringRef str) const {