Properly link flecs library

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

@@ -0,0 +1,54 @@
+#include <pipeline.h>
+#include <stdio.h>
+
+typedef struct {
+    double x, y;
+} Position, Velocity;
+
+void Move(ecs_iter_t *it) {
+    Position *p = ecs_field(it, Position, 1);
+    const Velocity *v = ecs_field(it, const Velocity, 2);
+
+    for (int i = 0; i < it->count; i ++) {
+        p[i].x += v[i].x;
+        p[i].y += v[i].y;
+    }
+}
+
+void PrintPosition(ecs_iter_t *it) {
+    const Position *p = ecs_field(it, const Position, 1);
+
+    for (int i = 0; i < it->count; i ++) {
+        printf("%s: {%f, %f}\n", ecs_get_name(it->world, it->entities[i]), 
+            p[i].x, p[i].y);
+    }
+}
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *ecs = ecs_init_w_args(argc, argv);
+
+    ECS_COMPONENT(ecs, Position);
+    ECS_COMPONENT(ecs, Velocity);
+
+    // Create system for moving an entity in the EcsOnUpdate phase
+    ECS_SYSTEM(ecs, Move, EcsOnUpdate, Position, [in] Velocity);
+
+    // Create system for printing a Position in the EcsPostUpdate phase
+    ECS_SYSTEM(ecs, PrintPosition, EcsPostUpdate, [in] Position);
+
+    // Create a few test entities for a Position, Velocity query
+    ecs_entity_t e1 = ecs_new_entity(ecs, "e1");
+    ecs_set(ecs, e1, Position, {10, 20});
+    ecs_set(ecs, e1, Velocity, {1, 2});
+
+    ecs_entity_t e2 = ecs_new_entity(ecs, "e2");
+    ecs_set(ecs, e2, Position, {10, 20});
+    ecs_set(ecs, e2, Velocity, {3, 4});
+
+    // Run the default pipeline. This will run all systems ordered by their
+    // phase. Systems within the same phase are ran in declaration order. This
+    // function is usually called in a loop.
+    ecs_progress(ecs, 0.0f);
+
+    return ecs_fini(ecs);
+}