Auto reinstall system apps on hide list

Since we are parsing through /data/app/ to find target APKs for
monitoring, system apps will not be covered in this case.
Automatically reinstall system apps as if they received an update
and refresh the monitor target after it's done.

As a bonus, use RAII idioms for locking pthread_mutex_t.

native/jni/utils/include/utils.h

@@ -150,6 +150,24 @@ std::vector<std::string> file_to_vector(const char *filename);
 
 // misc.cpp
 
+class MutexGuard {
+public:
+	explicit MutexGuard(pthread_mutex_t &m): mutex(&m) {
+		pthread_mutex_lock(mutex);
+	}
+
+	explicit MutexGuard(pthread_mutex_t *m): mutex(m) {
+		pthread_mutex_lock(mutex);
+	}
+
+	~MutexGuard() {
+		pthread_mutex_unlock(mutex);
+	}
+
+private:
+	pthread_mutex_t *mutex;
+};
+
 int new_daemon_thread(void *(*start_routine) (void *), void *arg = nullptr,
 		const pthread_attr_t *attr = nullptr);