tools/testing: add linux/args.h header and fix radix, VMA tests

Commit 857d18f ("cleanup: Introduce ACQUIRE() and ACQUIRE_ERR() for
conditional locks") accidentally broke the radix tree, VMA userland tests
by including linux/args.h which is not present in the tools/include
directory.

This patch copies this over and adds an #ifdef block to avoid duplicate
__CONCAT declaration in conflict with system headers when we ultimately
include this.

Link: https://lkml.kernel.org/r/20250811052654.33286-1-lorenzo.stoakes@oracle.com
Fixes: 857d18f ("cleanup: Introduce ACQUIRE() and ACQUIRE_ERR() for conditional locks") 
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: ljskernel

tools/include/linux/args.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_ARGS_H
+#define _LINUX_ARGS_H
+
+/*
+ * How do these macros work?
+ *
+ * In __COUNT_ARGS() _0 to _12 are just placeholders from the start
+ * in order to make sure _n is positioned over the correct number
+ * from 12 to 0 (depending on X, which is a variadic argument list).
+ * They serve no purpose other than occupying a position. Since each
+ * macro parameter must have a distinct identifier, those identifiers
+ * are as good as any.
+ *
+ * In COUNT_ARGS() we use actual integers, so __COUNT_ARGS() returns
+ * that as _n.
+ */
+
+/* This counts to 15. Any more, it will return 16th argument. */
+#define __COUNT_ARGS(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _n, X...) _n
+#define COUNT_ARGS(X...) __COUNT_ARGS(, ##X, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
+
+/* Concatenate two parameters, but allow them to be expanded beforehand. */
+#define __CONCAT(a, b) a ## b
+#define CONCATENATE(a, b) __CONCAT(a, b)
+
+#endif	/* _LINUX_ARGS_H */

tools/testing/shared/linux/idr.h

@@ -1 +1,5 @@
+/* Avoid duplicate definitions due to system headers. */
+#ifdef __CONCAT
+#undef __CONCAT
+#endif
 #include "../../../../include/linux/idr.h"