install_arch: verify bootstrap image signature

Fixes #458 (closed).

roles/install_arch/tasks/main.yml

@@ -50,11 +50,11 @@
     - https://geo.mirror.pkgbuild.com/iso/{{ bootstrap_version }}/archlinux-bootstrap-x86_64.tar.gz.sig
 
 - name: Get pierre's key
-  ansible.builtin.command: gpg --locate-keys pierre@archlinux.de
+  command: gpg --locate-keys pierre@archlinux.de
   changed_when: false
 
 - name: Get signature verification output
-  command: gpg --verify archlinux-bootstrap-x86_64.tar.gz.sig
+  command: gpg --verify /tmp/archlinux-bootstrap-x86_64.tar.gz.sig
   changed_when: false
 
 - name: Extract boostrap image  # noqa risky-file-permissions