[CMake] Cleanup uses of USES_TERMINAL
[CMake] Cleanup uses of USES_TERMINAL

Now that we are on CMake 3.4.3 we no longer need a version check around this.

This is the libcxx side of r272211.

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@272212 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx