Properly link flecs library

engine/libs/flecs/examples/c/prefabs/hierarchy/src/main.c

@@ -0,0 +1,38 @@
+#include <hierarchy.h>
+#include <stdio.h>
+
+// When a prefab has children, they are instantiated for an instance when the
+// IsA relationship to the prefab is added.
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *ecs = ecs_init_w_args(argc, argv);
+
+    // Create a prefab hierarchy.
+    ecs_entity_t SpaceShip = ecs_new_prefab(ecs, "SpaceShip");
+        ecs_entity_t SpaceShipEngine = ecs_new_prefab(ecs, "Engine");
+        ecs_add_pair(ecs, SpaceShipEngine, EcsChildOf, SpaceShip);
+    
+        ecs_entity_t SpaceShipCockpit = ecs_new_prefab(ecs, "Cockpit");
+        ecs_add_pair(ecs, SpaceShipCockpit, EcsChildOf, SpaceShip);
+
+    // Instantiate the prefab. This also creates an Engine and Cockpit child
+    // for the instance.
+    ecs_entity_t inst = ecs_new_entity(ecs, "my_spaceship");
+    ecs_add_pair(ecs, inst, EcsIsA, SpaceShip);
+    ecs_entity_t inst_engine = ecs_lookup_child(ecs, inst, "Engine");
+    ecs_entity_t inst_cockpit = ecs_lookup_child(ecs, inst, "Cockpit");
+
+    char *path = ecs_get_fullpath(ecs, inst_engine);
+    printf("instance engine:  %s\n", path);
+    ecs_os_free(path);
+
+    path = ecs_get_fullpath(ecs, inst_cockpit);
+    printf("instance cockpit: %s\n", path);
+    ecs_os_free(path);
+
+    // Output:
+    //  instance engine:  my_spaceship.Engine
+    //  instance cockpit: my_spaceship.Cockpit
+
+    return ecs_fini(ecs);
+}