Expose Engine::flush (#4385)

filament/include/filament/Engine.h

@@ -445,6 +445,8 @@ public:
      */
     void flushAndWait();
 
+    void flush();
+
     /**
      * Returns the default Material.
      *

filament/src/Engine.cpp

@@ -1026,6 +1026,10 @@ void Engine::flushAndWait() {
     upcast(this)->flushAndWait();
 }
 
+void Engine::flush() {
+    upcast(this)->flush();
+}
+
 utils::EntityManager& Engine::getEntityManager() noexcept {
     return upcast(this)->getEntityManager();
 }