[SYCL][HIP] Mark reduction_span_pack.cpp unsupported on hip/amd (#1079)

This test has been blocking the sycl pulldown for over a week and has evaded reproduction anywhere outside of CI. It's been decided to mark it xfail for now and continue with the pulldown as this problem is being investigated.

See intel/llvm#6409 for more details.

Author: dwoodwor-intel

SYCL/Reduction/reduction_span_pack.cpp

@@ -6,6 +6,11 @@
 // `Group algorithms are not supported on host device.` on Nvidia.
 // XFAIL: hip_nvidia
 
+// Disable this test on HIP/AMD until this issue has been fixed:
+// https://github.com/intel/llvm/issues/6409
+//
+// UNSUPPORTED: hip
+
 // This test performs basic checks of reductions initialized with a pack
 // containing at least one sycl::span