[OpenMP][Offloading] Enlarge the work size of wtime.c in case of any noise

Author: shiltian

openmp/libomptarget/test/offloading/wtime.c

@@ -6,19 +6,24 @@
 
 #include <omp.h>
 #include <stdio.h>
+#include <stdlib.h>
+
+#define N (1024 * 1024 * 256)
 
 int main(int argc, char *argv[]) {
-  int data[1024];
-#pragma omp target
+  int *data = (int *)malloc(N * sizeof(int));
+#pragma omp target map(from: data[0:N])
   {
     double start = omp_get_wtime();
-    for (int i = 0; i < 1024; ++i)
+    for (int i = 0; i < N; ++i)
       data[i] = i;
     double end = omp_get_wtime();
     double duration = end - start;
     printf("duration: %lfs\n", duration);
   }
+  free(data);
   return 0;
 }
 
 // CHECK: duration: {{.+[1-9]+}}
+