Remove extra MATCH_ variable sets when not neeeded.

This change increased the configure time for ParaView by 10 seconds. Without
the change 1,000,000 set to empty/ set to empty calls were being made. After
the change only 100,000 MATCH verables were set for the same code.
Merge topic 'remove_extra_matches' into next

01eaee7 Remove extra MATCH_ variable sets when not neeeded.