tools/nolibc: add limits.h shim header

limits.h is a widely used standard header. Missing it from nolibc requires
adoption effort to port applications.

Add a shim header which includes the global nolibc.h header.
It makes all nolibc symbols available.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Tested-by: Willy Tarreau <[e-mail]>
Reviewed-by: Vincenzo Frascino <[e-mail]>
Acked-by: Willy Tarreau <[e-mail]>
Acked-by: Shuah Khan <[e-mail]>
Link: https://lore.kernel.org/all/[e-mail]

tools/include/nolibc/Makefile

···
 		crt.h \
 		ctype.h \
 		errno.h \
+		limits.h \
 		nolibc.h \
 		signal.h \
 		stackprotector.h \

tools/include/nolibc/limits.h

···
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Shim limits.h header for NOLIBC.
+ * Copyright (C) 2025 Thomas Weißschuh <[e-mail]>
+ */
+
+#include "nolibc.h"