Properly link flecs library

engine/libs/flecs/examples/build/cmake/main.cpp

@@ -0,0 +1,40 @@
+#include "flecs.h"
+#include <iostream>
+
+/* Component types */
+struct Position {
+    double x, y;
+};
+
+struct Velocity {
+    double x, y;
+};
+
+int main(int argc, char *argv[]) {
+    flecs::world ecs(argc, argv);
+
+    ecs.system<Position, const Velocity>()
+        .iter([](const flecs::iter& it, 
+            Position *p, 
+            const Velocity *v) 
+        {    
+            for (auto row : it) {
+                p[row].x += v[row].x;
+                p[row].y += v[row].y;
+
+                std::cout << "Moved " << it.entity(row).name() << " to {" <<
+                    p[row].x << ", " << p[row].y << "}" << std::endl;
+            }
+        });
+
+    ecs.entity("MyEntity")
+        .set<Position>({0, 0})
+        .set<Velocity>({1, 1});
+
+    ecs.set_target_fps(1);
+
+    std::cout << "Application move_system is running, press CTRL-C to exit..." << std::endl;
+
+    /* Run systems */
+    while (ecs.progress()) { }
+}