package/attr: add missing libgen.h header

Resolves the following error when building against MUSL:

tools/attr.c: In function 'main':
tools/attr.c:69:20: error: implicit declaration of function 'basename'
[-Wimplicit-function-declaration]
   69 |         progname = basename(argv[0]);
      |                    ^~~~~~~~
tools/attr.c:69:18: error: assignment to 'char *' from 'int' makes
pointer from integer without a cast [-Wint-conversion]
   69 |         progname = basename(argv[0]);
      |                  ^

Upstream: https://git.savannah.nongnu.org/cgit/attr.git/commit/?id=8a80d895dfd779373363c3a4b62ecce5a549efb2

Fixes: http://autobuild.buildroot.net/results/c61206968eda9913e37e95a61dc3e10399503fcd/

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
[Romain: use upstream patch]
Signed-off-by: Romain Naour <romain.naour@smile.fr>
(cherry picked from commit fa241685e7f92311f5fd50ce17c1541748fe285b)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/attr/0003-tools-attr.c-Add-missing-libgen.h-include-for-basena.patch

@@ -0,0 +1,32 @@
+From 8a80d895dfd779373363c3a4b62ecce5a549efb2 Mon Sep 17 00:00:00 2001
+From: "Haelwenn (lanodan) Monnier" <contact@hacktivis.me>
+Date: Sat, 30 Mar 2024 10:17:10 +0100
+Subject: [PATCH] tools/attr.c: Add missing libgen.h include for basename(3)
+
+Fixes compilation issue with musl and modern C99 compilers.
+
+See: https://bugs.gentoo.org/926294
+
+Upstream: https://git.savannah.nongnu.org/cgit/attr.git/commit/?id=8a80d895dfd779373363c3a4b62ecce5a549efb2
+
+Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
+Signed-off-by: Romain Naour <romain.naour@smile.fr>
+---
+ tools/attr.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/tools/attr.c b/tools/attr.c
+index f12e4af..6a3c1e9 100644
+--- a/tools/attr.c
++++ b/tools/attr.c
+@@ -28,6 +28,7 @@
+ #include <errno.h>
+ #include <string.h>
+ #include <locale.h>
++#include <libgen.h>
+ 
+ #include <attr/attributes.h>
+ 
+-- 
+2.45.0
+