Properly link flecs library

engine/libs/flecs/examples/c/systems/startup_system/src/main.c

@@ -0,0 +1,42 @@
+#include <startup_system.h>
+#include <stdio.h>
+
+// Startup systems are systems registered with the EcsOnStart phase, and are
+// only ran during the first frame. Just like with regular phases, custom phases
+// can depend on the EcsOnStart phase (see custom_phases example). Phases that 
+// depend on EcsOnStart are also only ran during the first frame.
+//
+// Other than that, startup systems behave just like regular systems (they can
+// match components, can introduce merge points), with as only exception that
+// they are guaranteed to always run on the main thread. 
+
+void Startup(ecs_iter_t *it) {
+    printf("%s\n", ecs_get_name(it->world, it->system));
+}
+
+void Update(ecs_iter_t *it) {
+    printf("%s\n", ecs_get_name(it->world, it->system));
+}
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *ecs = ecs_init_w_args(argc, argv);
+
+    // Startup system
+    ECS_SYSTEM(ecs, Startup, EcsOnStart, 0);
+
+    // Regular system
+    ECS_SYSTEM(ecs, Update, EcsOnUpdate, 0);
+
+    // First frame. This runs both the Startup and Update systems
+    ecs_progress(ecs, 0.0f);
+
+    // Second frame. This runs only the Update system
+    ecs_progress(ecs, 0.0f);
+
+    return ecs_fini(ecs);
+
+    // Output
+    //   Startup
+    //   Update
+    //   Update
+}