Properly link flecs library

engine/libs/flecs/examples/cpp/entities/iterate_components/src/main.cpp

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+#include <iterate_components.h>
+#include <iostream>
+
+// Ordinary components
+struct Position {
+    double x, y;
+};
+
+struct Velocity {
+    double x, y;
+};
+
+// Tag
+struct Human { };
+
+// Two tags used to create a pair
+struct Eats { };
+struct Apples { };
+
+void iterate_components(flecs::entity e) {
+    // 1. The easiest way to print the components is to use type::str
+    std::cout << e.type().str() << "\n\n";
+
+    // 2. To get individual component ids, use entity::each
+    int32_t i = 0;
+    e.each([&](flecs::id id) {
+        std::cout << i++ << ": " << id.str() << "\n";
+    });
+    std::cout << "\n";
+
+    // 3. we can also inspect and print the ids in our own way. This is a
+    // bit more complicated as we need to handle the edge cases of what can be
+    // encoded in an id, but provides the most flexibility.
+    i = 0;
+    e.each([&](flecs::id id) {
+        std::cout << i++ << ": ";
+
+        if (id.is_pair()) {
+            // If id is a pair, extract & print both parts of the pair
+            flecs::entity rel = id.first();
+            flecs::entity tgt = id.second();
+            std::cout << "rel: " << rel.name() << ", " << "tgt: " << tgt.name();
+        } else {
+            // Id contains a regular entity. Strip role before printing.
+            flecs::entity comp = id.entity();
+            std::cout << "entity: " << comp.name();
+        }
+
+        std::cout << "\n";
+    });
+
+    std::cout << "\n\n";
+}
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    flecs::entity bob = ecs.entity()
+        .set<Position>({10, 20})
+        .set<Velocity>({1, 1})
+        .add<Human>()
+        .add<Eats, Apples>();
+
+    std::cout << "Bob's components:\n";
+    iterate_components(bob);
+
+    // We can use the same function to iterate the components of a component
+    std::cout << "Position's components:\n";
+    iterate_components(ecs.component<Position>());
+}
+
+// Output:
+
+// Bob's components:
+// Position, Velocity, Human, (Eats,Apples)
+// 
+// 0: Position
+// 1: Velocity
+// 2: Human
+// 3: (Eats,Apples)
+// 
+// 0: entity: Position
+// 1: entity: Velocity
+// 2: entity: Human
+// 3: rel: Eats, tgt: Apples
+// 
+// 
+// Position's components:
+// Component, (Identifier,Name), (Identifier,Symbol), (OnDelete,Panic)
+// 
+// 0: Component
+// 1: (Identifier,Name)
+// 2: (Identifier,Symbol)
+// 3: (OnDelete,Panic)
+// 
+// 0: entity: Component
+// 1: rel: Identifier, tgt: Name
+// 2: rel: Identifier, tgt: Symbol
+// 3: rel: OnDelete, tgt: Panic