build: Call 'systemd-tmpfiles --create' when installing

It's only necessary to call 'systemd-tmpfiles --create' when building
and installing from source, and not when using a downstream package,
because:

  * When 'meson install' is called as part of building the package,
    that's not when the temporary files need to be created. They need
    to be created when the package is later downloaded and installed
    by the user.

  * Downstream tools can sometimes handle it automatically. eg., on
    Fedora, the systemd RPM installs a trigger that tells RPM to call
    'systemd-tmpfiles --create' automatically when a tmpfiles.d snippet
    is installed.

containers#955

meson.build

@@ -65,3 +65,5 @@ subdir('data')
 subdir('doc')
 subdir('profile.d')
 subdir('src')
+
+meson.add_install_script('meson_post_install.py')

meson_post_install.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python3
+
+import os
+import subprocess
+
+destdir = os.environ.get('DESTDIR', '')
+
+if not destdir:
+    print('Calling systemd-tmpfiles --create ...')
+    subprocess.call(['systemd-tmpfiles', '--create'])

playbooks/setup-env.yaml

@@ -52,10 +52,3 @@
       args:
         chdir: '{{ zuul.project.src_dir }}'
         creates: /usr/local/bin/toolbox
-
-    - name: Setup environment
-      become: yes
-      command:
-        cmd: systemd-tmpfiles --create
-        creates: /run/media
-        creates: /run/host