Basics: only allow ASTContext to add block list path

Author: nkcsgexi

include/swift/Basic/BlockList.h

@@ -38,10 +38,11 @@ class BlockListStore {
   struct Implementation;
   bool hasBlockListAction(StringRef key, BlockListKeyKind keyKind,
                           BlockListAction action);
-  void addConfigureFilePath(StringRef path);
   BlockListStore();
   ~BlockListStore();
 private:
+  friend class ASTContext;
+  void addConfigureFilePath(StringRef path);
   Implementation &Impl;
 };