tools/nolibc: move NULL and offsetof() to sys/stddef.h

This is the location regular userspace expects these definitions.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Acked-by: Willy Tarreau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

tools/include/nolibc/Makefile

···
 		std.h \
 		stdarg.h \
 		stdbool.h \
+		stddef.h \
 		stdint.h \
 		stdlib.h \
 		string.h \

tools/include/nolibc/std.h

···
  * syscall-specific stuff, as this file is expected to be included very early.
  */
 
-/* note: may already be defined */
-#ifndef NULL
-#define NULL ((void *)0)
-#endif
-
 #include "stdint.h"
+#include "stddef.h"
 
 /* those are commonly provided by sys/types.h */
 typedef unsigned int          dev_t;

tools/include/nolibc/stddef.h

···
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Stddef definitions for NOLIBC
+ * Copyright (C) 2017-2021 Willy Tarreau <[e-mail]>
+ */
+
+/* make sure to include all global symbols */
+#include "nolibc.h"
+
+#ifndef _NOLIBC_STDDEF_H
+#define _NOLIBC_STDDEF_H
+
+#include "stdint.h"
+
+/* note: may already be defined */
+#ifndef NULL
+#define NULL ((void *)0)
+#endif
+
+#ifndef offsetof
+#define offsetof(TYPE, FIELD) ((size_t) &((TYPE *)0)->FIELD)
+#endif
+
+#endif /* _NOLIBC_STDDEF_H */

tools/include/nolibc/types.h

···
 typedef __kernel_clockid_t clockid_t;
 typedef int timer_t;
 
-#ifndef offsetof
-#define offsetof(TYPE, FIELD) ((size_t) &((TYPE *)0)->FIELD)
-#endif
-
 #ifndef container_of
 #define container_of(PTR, TYPE, FIELD) ({			\
 	__typeof__(((TYPE *)0)->FIELD) *__FIELD_PTR = (PTR);	\