[llvm] [libsycl] Add lit configuration files and basic test (PR #177407)

[Kseniya Tikhomirova via llvm-commits]

KseniyaTikhomirova wrote:

> Sorry to be a pain but do you mind pinging me once Dmitry's feedback is addressed so I can take a final look? Thanks

sure, no pain, I appreciate the review.

https://github.com/llvm/llvm-project/pull/177407