flatpak: add system helper user

Closes #13155

srcpkgs/flatpak/template

@@ -1,10 +1,13 @@
 # Template file for 'flatpak'
 pkgname=flatpak
 version=1.4.2
-revision=1
+revision=2
 build_style=gnu-configure
 build_helper="gir"
-configure_args="--disable-documentation --with-system-bubblewrap
+configure_args="
+ --disable-documentation
+ --with-system-bubblewrap
+ --with-system-helper-user=_flatpak
  $(vopt_enable gir introspection)"
 hostmakedepends="bubblewrap glib-devel libxslt pkg-config bison"
 makedepends="appstream-glib-devel gpgme-devel json-glib-devel libcap-devel
@@ -22,6 +25,8 @@ checksum=f2799a6d973a052529b52943021108f148706d3e69725ac7dd60bf6ac4bdd522
 build_options="gir"
 build_options_default="gir"
 
+system_accounts="_flatpak"
+
 if [ "$CROSS_BUILD" ]; then
 	configure_args+=" --enable-selinux-module=no"
 fi