Add '+' to the list of accepted characters in kbas artifacts
Fixes:
[libdbus-c++] Starting upload
[libdbus-c++] Artifact server problem: 400
[libdbus-c++] Failed to upload libdbus-c++.joidja8
See #256
Fixes:
[libdbus-c++] Starting upload
[libdbus-c++] Artifact server problem: 400
[libdbus-c++] Failed to upload libdbus-c++.joidja8
See #256