flatpak fails to build in Leap's staging C
https://build.opensuse.org/package/show/openSUSE:Leap:15.2:Staging:C/flatpak ,
it looks like because systemd hasn't pulled into buildroot, in the past,
systemd was pulled by polkit however with a updated polkit no longer hard
requires systemd. The solution can be add pkgconfig(systemd).

The full build log:
https://build.opensuse.org/package/live_build_log/openSUSE:Leap:15.2:Staging:C/flatpak/standard/x86_64

Bug ID	1159894
Summary	flatpak fails to build in 15.2
Classification	openSUSE
Product	openSUSE Distribution
Version	Leap 15.2
Hardware	Other
OS	Other
Status	NEW
Severity	Normal
Priority	P5 - None
Component	GNOME
Assignee	gnome-bugs@suse.de
Reporter	mlin@suse.com
QA Contact	qa-bugs@suse.de
Found By	---
Blocker	---