archweb: set gpg_whitelist to archweb signed key

ansible 2.9.0 has a new git module feature gpg_whitelist which is an
array of allowed keys. If a tag or commit was signed with a different
key ansible aborts.

Signed-off-by: Jelle van der Waa <jelle@archlinux.org>

roles/archweb/defaults/main.yml

@@ -9,6 +9,7 @@ archweb_domains_redirects:
 archweb_nginx_conf: '/etc/nginx/nginx.d/archweb.conf'
 archweb_repository: 'https://github.com/archlinux/archweb.git'
 archweb_version: release_2019-10-25
+archweb_pgp_key: ['E499C79F53C96A54E572FEE1C06086337C50773E']
 archweb_site: true
 archweb_mirrorcheck: false
 archweb_mirrorresolv: false

roles/archweb/tasks/main.yml

@@ -42,6 +42,7 @@
     dest="{{ archweb_dir }}"
     version={{ archweb_version }}
     verify_commit=true
+    gpg_whitelist={{ archweb_pgp_key }}
   become: true
   become_user: archweb
   register: release