Fix Unix build error due to issue in `tools/unix/get-source-version.sh`.
Fix Unix build error due to issue in `tools/unix/get-source-version.sh`.

LeForgeron/povray,POV-Ray/povray,LeForgeron/povray,LeForgeron/povray,LeForgeron/povray,POV-Ray/povray,wfpokorny/povray,POV-Ray/povray,c-lipka/povray,POV-Ray/povray,wfpokorny/povray,POV-Ray/povray,LeForgeron/povray,LeForgeron/povray,LeForgeron/povray,wfpokorny/povray,c-lipka/povray,LeForgeron/povray,c-lipka/povray,wfpokorny/povray,c-lipka/povray,wfpokorny/povray,POV-Ray/povray,wfpokorny/povray,wfpokorny/povray,POV-Ray/povray