libostree: update to 2017.15.
libostree: update to 2017.15.

Closes: #10146 [via git-merge-pr]

floGik/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,coredumb/void-packages,coredumb/void-packages,floGik/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,floGik/void-packages,floGik/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,coredumb/void-packages,floGik/void-packages,NeoChontrix/void-packages,coredumb/void-packages,NeoChontrix/void-packages,coredumb/void-packages,floGik/void-packages,necrophcodr/void-packages,coredumb/void-packages