rusticl: release borrow on device build before linking

This allows for a later refactor to share linking code between
clBuildProgram and clLinkProgram in which the device build is borrowed
mutably.

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36497>

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

@@ -583,7 +583,8 @@ impl Program {
                 }
             }
 
-            let spirvs = [d.spirv.as_ref().unwrap()];
+            let spirv = d.spirv.take().unwrap();
+            let spirvs = [&spirv];
             let (spirv, log) = spirv::SPIRVBin::link(&spirvs, lib);
 
             d.log.push_str(&log);