[cmake] Pass through the cmake_3_2_USES_TERMINAL variable so we get progress...

[cmake] Pass through the cmake_3_2_USES_TERMINAL variable so we get progress bars on an external compiler-rt build

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@262336 91177308-0d34-0410-b5e6-96231b3b80d8