Haiku port of duckstation libretro core (#716)

* Haiku build 1st attempt

* fix load on Haiku

* Removed debugging flags

* Added a couple ifndef

src/common/event.h

@@ -19,7 +19,7 @@ public:
 private:
 #ifdef WIN32
   void* m_event_handle;
-#elif defined(__linux__) || defined(__APPLE__)
+#elif defined(__linux__) || defined(__APPLE__) || defined(__HAIKU__)
   int m_pipe_fds[2];
   bool m_auto_reset;
 #else
@@ -27,4 +27,4 @@ private:
 #endif
 };
 
-} // namespace Common
+} // namespace Common