Hello, I'm the maintainer of :
I had to apply the following patch to fix urbackup not building into Arch Linux.
P.S: you should add a link to here to your GitHub repository or at least allow issue there... I'm personally not friendly with this interface but maybe it's because it's the first time I have to answer so much unnecessary question to fill a patch/issue ...
P.S: I'm not going to answer directly as it's the first time and maybe the last time I'll be here so for further information/questions please report to firstname.lastname@example.org