dpclang compiler identification in cmake

With https://github.com/intel/llvm/commit/165a5285e21dad02984661c302df99cc99ade822 (tip of [sycl-rel-7_0](https://github.com/intel/llvm/compare/sycl-rel-7_0) branch as of 6/4/2026). On the project using cmake. For example:
```
$ cat CMakeLists.txt
cmake_minimum_required(VERSION 3.14)
project(test LANGUAGES C CXX)
```
The configuration output will look like the following:
```
$ CC=dpclang CXX=dpclang++ cmake ..
-- The C compiler identification is Clang 22.1.0
-- The CXX compiler identification is Clang 22.1.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /home/dvrogozh/git/intel-llvm/build/install/bin/dpclang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /home/dvrogozh/git/intel-llvm/build/install/bin/dpclang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.9s)
-- Generating done (0.0s)
-- Build files have been written to: /home/dvrogozh/tmp/ccc/_build
```

Question: should dpclang compiler identification recognized by cmake actually be `Clang 22.1.0` and check for working C/CXX compiler skipped?

That's not necessarily a bug, but I thought I will raise this as a question.

CC: @tahonermann @sarnex