[SYCL][CUDA] Avoid failure when no devices available

[Ruyk]

cuInit fails when there are no CUDA devices, but this
is not an error for the SYCL runtime.
This patch converts the error into a platform with no devices.

[fwyzard]

According to the latest SYCL specification (4.6.2 Platform clas)

A SYCL platform is also associated with one or more SYCL devices

So, would it make more sense not to return the platform at all, rather than a platform without any device ?

[fwyzard]

See #1212 for an alternative fix.

[Ruyk]

According to the latest SYCL specification (4.6.2 Platform clas)

A SYCL platform is also associated with one or more SYCL devices

So, would it make more sense not to return the platform at all, rather than a platform without any device ?

That may change in the future with the backend model, since you may want to differentiate when a backend is active but there are no devices (hence, empty platform) from when the backend is not active (so, no platform from that backend appears).
But, this is a SYCL 1.2.1 implementation so you are correct, your fix in #1212 is better, thanks!

[keryell]

That may change in the future with the backend model, since you may want to differentiate when a backend is active but there are no devices (hence, empty platform) from when the backend is not active (so, no platform from that backend appears).

Good idea. Keep track of this!