shut up clang warnings

- Fix some class/struct discrepancies
- Explicit the overloading of `run` in the `Cmd*` classes
- Ignore a warning in the generated lexer

src/libstore/build/goal.hh

@@ -7,7 +7,7 @@ namespace nix {
 
 /* Forward definition. */
 struct Goal;
-struct Worker;
+class Worker;
 
 /* A pointer to a goal. */
 typedef std::shared_ptr<Goal> GoalPtr;

src/libstore/build/worker.hh

@@ -8,8 +8,8 @@
 namespace nix {
 
 /* Forward definition. */
-class DerivationGoal;
-class SubstitutionGoal;
+struct DerivationGoal;
+struct SubstitutionGoal;
 
 /* Workaround for not being able to declare a something like
 

src/libstore/local-store.hh

@@ -296,8 +296,8 @@ private:
 
     void createUser(const std::string & userName, uid_t userId) override;
 
-    friend class DerivationGoal;
-    friend class SubstitutionGoal;
+    friend struct DerivationGoal;
+    friend struct SubstitutionGoal;
 };