fix ansible quoting issues

Change-Id: I2a9043a843be9d26df733f3edc2bb3e944ae8af5
diff --git a/ansible/roles/buildtools/tasks/main.yml b/ansible/roles/buildtools/tasks/main.yml
index a147e6e..6c0e3faf 100644
--- a/ansible/roles/buildtools/tasks/main.yml
+++ b/ansible/roles/buildtools/tasks/main.yml
@@ -1,6 +1,6 @@
 - name: Apt packages
   apt:
     name: "{{ item }}"
-  with_items: apt_packages
+  with_items: "{{ apt_packages }}"
   tags: [buildtools]