seems appdata/subsurface.appdata.xml in the repo is edited during build

[Cristian Ionescu-Idbohrn]

$ git status
...
modified: appdata/subsurface.appdata.

$ git diff
...
- <release version="" date="" />
+ <release version="v4.8.1-402-gc3bd10e36af5" date="2018-09-12" />


Cheers,