Properly link flecs library

engine/libs/flecs/BUILD

@@ -0,0 +1,9 @@
+
+cc_library(
+    name = "flecs",
+    visibility = ["//visibility:public"],
+
+    srcs = glob(["src/**/*.c", "src/**/*.h", "src/**/*.inl"]),
+    hdrs = glob(["include/**/*.h", "include/**/*.hpp", "include/**/*.inl"]),
+    includes = ["include"],
+)