health: do not use default destructor.

Otherwise, clients will need to know how to destroy
LinkedCallback, a hidden class.

Test: builds
Bug: 177269435
Change-Id: I89532755da16b672c4cbece55b943306f68cdb9e
diff --git a/health/aidl/default/Health.cpp b/health/aidl/default/Health.cpp
index 812e64a..e1d1982 100644
--- a/health/aidl/default/Health.cpp
+++ b/health/aidl/default/Health.cpp
@@ -60,6 +60,8 @@
     battery_monitor_.init(healthd_config_.get());
 }
 
+Health::~Health() {}
+
 //
 // Getters.
 //
diff --git a/health/aidl/default/include/health-impl/Health.h b/health/aidl/default/include/health-impl/Health.h
index e49f44c..6bd4946 100644
--- a/health/aidl/default/include/health-impl/Health.h
+++ b/health/aidl/default/include/health-impl/Health.h
@@ -43,6 +43,7 @@
     // A subclass may modify |config| before passing it to the parent constructor.
     // See implementation of Health for code samples.
     Health(std::string_view instance_name, std::unique_ptr<struct healthd_config>&& config);
+    virtual ~Health();
 
     ndk::ScopedAStatus registerCallback(
             const std::shared_ptr<IHealthInfoCallback>& callback) override;