cmake: remove unnecessary check for getenv()
cmake: remove unnecessary check for getenv()

autotools does not currently check for getenv(), so there
is nothing to do if it is actually missing.

git-svn-id: ae38cf1093b87151f738d2b2220cac7742ad2e55@985 64e312b2-a51f-0410-8e61-82d0ca0eb02a

lubosz/check,lubosz/check,lubosz/check,lubosz/check