Derive the right paths to use during testing instead of passing it in via make.

Also, fix a few other details of the cmake test target and rename it to
'check'. CMake tests now work for the most part, but there are a handful of
failures left due to missing site.exp bits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86452 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed