[SYCL] Loading of free function kernels does not work with PTX

[lbushi25]

Describe the bug

The E2E tests

sycl/test-e2e/KernelAndProgram/free_function_apis.cpp
sycl/test-e2e/KernelAndProgram/free_function_kernels.cpp
sycl/test-e2e/DeviceImageDependencies/free_function_kernels.cpp

fail on CUDA and there are comments saying this is due to name mangling for free function kernels not working with PTX.
The error logs as seen in the CUDA CI run of this PR(#16081) say that an exception is thrown with a kernel not found error so this may or may not be a name mangling issue. More investigation is needed.

To reproduce

Simply run llvm-lit with the tests above on a CUDA platform. As access to a CUDA platform may be hard to get, usually I will simply submit a draft PR where I remove the UNSUPPORTED directive from one of these tests and then look at the CI results for the CUDA runner.

Environment

• OS: Any
• Target device and vendor: CUDA
• DPC++ version: dc181bb (latest commit as of writing this)
• Dependencies version: [e.g. the output of sycl-ls --verbose]

Additional context

No response

[tahonermann]

@lbushi25, please rename this issue in order to prevent further confusion. As discussed elsewhere, the problem doesn't appear to be related to name mangling.