[SYCL][CUDA] fix warnings in async barrier (#6165)

Fixes warnings introduced in #5303.

Co-authored-by: Artur Gainullin <artur.gainullin@intel.com>

Author: t4c1

sycl/include/sycl/ext/oneapi/experimental/cuda/barrier.hpp

@@ -32,6 +32,8 @@ class barrier {
 #ifdef __SYCL_DEVICE_ONLY__
     __clc_BarrierInitialize(&state, expected_count);
 #else
+    (void)state;
+    (void)expected_count;
     throw runtime_error("Barrier is not supported on host device.",
                         PI_INVALID_DEVICE);
 #endif
@@ -68,6 +70,7 @@ class barrier {
 #ifdef __SYCL_DEVICE_ONLY__
     return __clc_BarrierArriveNoComplete(&state, count);
 #else
+    (void)count;
     throw runtime_error("Barrier is not supported on host device.",
                         PI_INVALID_DEVICE);
 #endif
@@ -77,6 +80,7 @@ class barrier {
 #ifdef __SYCL_DEVICE_ONLY__
     return __clc_BarrierArriveAndDropNoComplete(&state, count);
 #else
+    (void)count;
     throw runtime_error("Barrier is not supported on host device.",
                         PI_INVALID_DEVICE);
 #endif
@@ -104,6 +108,7 @@ class barrier {
 #ifdef __SYCL_DEVICE_ONLY__
     __clc_BarrierWait(&state, arrival);
 #else
+    (void)arrival;
     throw runtime_error("Barrier is not supported on host device.",
                         PI_INVALID_DEVICE);
 #endif
@@ -113,6 +118,7 @@ class barrier {
 #ifdef __SYCL_DEVICE_ONLY__
     return __clc_BarrierTestWait(&state, arrival);
 #else
+    (void)arrival;
     throw runtime_error("Barrier is not supported on host device.",
                         PI_INVALID_DEVICE);
 #endif