Update building_os.md

pages/building_os.md

@@ -88,3 +88,5 @@ The Pi-KVM OS is based on Arch Linux ARM and contains all the required packages
 11. **27.08.2020 note about systemd**: the latest version of Arch Linux has a slightly broken systemd. The problem is that SSH to the Pi-KVM host may not work the first time, but the second or third. The Pi-KVM build environment contains a workaround for this problem: in the file `/etc/pam.d/system-login` line `-session   optional   pam_systemd.so` is commented. This does not have any negative impact on the PI-KVM functionality, but if you want to, after fixing the systemd (in a couple of months with the next update), you can uncomment this line.
 
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