veristat: avoid using kernel-internal headers

Drop linux/compiler.h include, which seems to be needed for ARRAY_SIZE
macro only. Redefine own version of ARRAY_SIZE instead.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230331222405.3468634-4-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/veristat.c

@@ -4,7 +4,6 @@
 #include <argp.h>
 #include <string.h>
 #include <stdlib.h>
-#include <linux/compiler.h>
 #include <sched.h>
 #include <pthread.h>
 #include <dirent.h>
@@ -20,6 +19,10 @@
 #include <gelf.h>
 #include <float.h>
 
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+#endif
+
 enum stat_id {
 	VERDICT,
 	DURATION,