tests/datawizard/variable_size.c: insert user name in directory name to avoid conflicts

tests/datawizard/variable_size.c

@@ -255,9 +255,12 @@ int main(int argc, char **argv)
 	int i;
 	int x, y;
 	starpu_data_handle_t handles[N][N];
+	char s[128];
+
+	snprintf(s, sizeof(s), "/tmp/%s-variable_size", getenv("USER"));
 
 	setenv("STARPU_LIMIT_CPU_MEM", LIMIT, 1);
-	setenv("STARPU_DISK_SWAP", "/tmp/starpu-variable_size", 0);
+	setenv("STARPU_DISK_SWAP", s, 0);
 	setenv("STARPU_DISK_SWAP_SIZE", "100000", 1);
 #ifdef STARPU_LINUX_SYS
 	setenv("STARPU_DISK_SWAP_BACKEND", "unistd_o_direct", 0);