build: add flatpak option to install demo wrapper

.build_files/meson.build

@@ -14,3 +14,11 @@ translators = run_command(
   'cat', files('translators'),
 ).stdout().strip()
 
+if get_option('flatpak')
+  # start in demo mode when using flatpak through wrapper
+  demo_script = files('os-installer-demo')
+
+  install_data(demo_script,
+    install_dir: get_option('bindir')
+  )
+endif

.build_files/os-installer-demo

@@ -0,0 +1,2 @@
+#!/bin/sh
+exec os-installer -d

meson_options.txt

@@ -0,0 +1 @@
+option('flatpak', type: 'boolean', value: false, description: 'Build with flatpak, install demo mode wrapper')