attr: add patch solving portability issues when using a libc which is not providing cdefs.h

This is the case for musl libc

base/attr/0002-cdefs.patch

@@ -0,0 +1,43 @@
+# --- SDE-COPYRIGHT-NOTE-BEGIN ---
+# This copyright note is auto-generated by ./scripts/Create-CopyPatch.
+#
+# Filename: package/.../attr/0002-cdefs.patch
+# Copyright (C) 2013 The OpenSDE Project
+#
+# More information can be found in the files COPYING and README.
+#
+# This patch file is dual-licensed. It is available under the license the
+# patched project is licensed under, as long as it is an OpenSource license
+# as defined at http://www.opensource.org/ (e.g. BSD, X11) or under the terms
+# of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+# --- SDE-COPYRIGHT-NOTE-END ---
+
+--- a/include/xattr.h
++++ b/include/xattr.h
+@@ -30,8 +30,13 @@
+ #define XATTR_CREATE  0x1       /* set value, fail if attr already exists */
+ #define XATTR_REPLACE 0x2       /* set value, fail if attr does not exist */
+ 
++#ifndef __THROW
++#define __THROW
++#endif
+ 
+-__BEGIN_DECLS
++#ifdef __cplusplus
++extern "C" {
++#endif
+ 
+ extern int setxattr (const char *__path, const char *__name,
+ 		      const void *__value, size_t __size, int __flags) __THROW;
+@@ -58,6 +63,8 @@
+ extern int lremovexattr (const char *__path, const char *__name) __THROW;
+ extern int fremovexattr (int __filedes,   const char *__name) __THROW;
+ 
+-__END_DECLS
++#ifdef __cplusplus
++}
++#endif
+ 
+ #endif	/* __XATTR_H__ */