rusticl/kernel: Fix creation from programs not built for every device

OpenCL does not require that a kernel is created for every device. So we
shouldn't assume there is a build for every device.

API validation around launching kernels already takes this possibility
into account.

I did not verify if the commit below is actually the culprit and whether
this bug existed before that, but a fix for older code also would have to
look differently anyway.

Fixes: 323dcbb4b5 ("rusticl: Move NirKernelBuild to ProgramDevBuild")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9968
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25696>

src/gallium/frontends/rusticl/core/kernel.rs

@@ -788,7 +788,7 @@ impl Kernel {
         let builds = prog_build
             .builds
             .iter()
-            .map(|(k, v)| (*k, v.kernels.get(&name).unwrap().clone()))
+            .filter_map(|(&dev, b)| b.kernels.get(&name).map(|k| (dev, k.clone())))
             .collect();
 
         // can't use vec!...