Properly link flecs library

engine/libs/flecs/examples/cpp/hello_world/src/main.cpp

@@ -0,0 +1,50 @@
+#include <hello_world.h>
+#include <iostream>
+
+// Component types
+struct Position {
+    double x;
+    double y;
+};
+
+struct Velocity {
+    double x;
+    double y;
+};
+
+// Tag types
+struct Eats { };
+struct Apples { };
+
+int main(int, char *[]) {
+    // Create the world
+    flecs::world ecs;
+
+    // Register system
+    ecs.system<Position, Velocity>()
+        .each([](Position& p, Velocity& v) {
+            p.x += v.x;
+            p.y += v.y;
+        });
+
+    // Create an entity with name Bob, add Position and food preference
+    flecs::entity Bob = ecs.entity("Bob")
+        .set(Position{0, 0})
+        .set(Velocity{1, 2})
+        .add<Eats, Apples>();
+
+    // Show us what you got
+    std::cout << Bob.name() << "'s got [" << Bob.type().str() << "]\n";
+
+    // Run systems twice. Usually this function is called once per frame
+    ecs.progress();
+    ecs.progress();
+
+    // See if Bob has moved (he has)
+    const Position *p = Bob.get<Position>();
+    std::cout << Bob.name() << "'s position is {" << p->x << ", " << p->y << "}\n";
+
+    // Output
+    //  Bob's got [Position, Velocity, (Identifier,Name), (Eats,Apples)]
+    //  Bob's position is {2, 4}
+}