[SYCL][NFCI] Move abs and div to cstdlib header

[bader]

These functions are declared in cmath and use data type defined in
cstdlib. Some cmath implementations include cstdlib implicitly, but
not all of them. Moving declarations to a standalone header removes
dependency on cmath implementation.

[bader]

run_prebuilt_e2e_tests (E2E tests on Intel Ponte Vecchio GPU, ["Linux", "pvc"], -u 1001 --device=... / E2E tests on Intel Ponte Vecchio GPU failure doesn't seem to be related to the change. The test doesn't use abs or div functions and there is known issue with this test on PVC. See #19662.

[jinge90]

Hi, @bader
Can we keep the functions in libdevice? They are used by OMP offloading as well.
If can't, we can only build them for OMP offloading side.
Thanks very much.

[bader]

Can we keep the functions in libdevice? They are used by OMP offloading as well. If can't, we can only build them for OMP offloading side. Thanks very much.

There is no sense in making any changes for OpenMP offloading in this repository because OpenMP offloading is not supported/tested here.

In the upstream OpenMP offloading uses clang's headers to implement abs on AMD GPU. I suggest using the same approach for SPIR-V targets in other repositories as well.
The same applies to div if it's needed for OpenMP offloading.

@sarnex, are you working on something similar in the upstream?

[Maetveis]

This will conflict with #19620. Can you apply the changes here I did to these functions, I don't want it to be lost during conflict resolution.

[sarnex]

@sarnex, are you working on something similar in the upstream?

I haven't begun to think about how we will deal with libdevice in OMP upstream, however I agree we should match whatever the community does as best as possible.