pdnsd-alt: fix kernel 5.15 build error (#8557)

Co-authored-by: SiYao Mo <msylgj@vip.qq.com>

package/lean/pdnsd-alt/patches/002-fix-pdnsd-alt-build-error-within-kernel_5.15.patch

@@ -0,0 +1,39 @@
+From 59859acf9083010639eb9bc0bf8cb5d03f03935f Mon Sep 17 00:00:00 2001
+From: SiYao Mo <msylgj@vip.qq.com>
+Date: Fri, 16 Jul 2021 14:25:44 +0800
+Subject: [PATCH] pdnsd-alt: fix cmake error in kernel 5.15 Because of
+ redefinition of 'struct ifmap' & 'struct ifreq' & 'struct ifconf' in
+ linux/if.h (Linux Kernel above 5.13) Replace net/if.h with linux/if.h
+
+Signed-off-by: SiYao Mo <msylgj@vip.qq.com>
+---
+ src/conff.h | 2 +-
+ src/dns.h   | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/src/conff.h b/src/conff.h
+index a07b156..c66d210 100644
+--- a/src/conff.h
++++ b/src/conff.h
+@@ -32,7 +32,7 @@
+ #include <stdio.h>
+ #include <pthread.h>
+ #include <sys/socket.h>
+-#include <net/if.h>
++#include <linux/if.h>
+ #include "ipvers.h"
+ #include "list.h"
+ 
+diff --git a/src/dns.h b/src/dns.h
+index 0f6a4ac..ecc9680 100644
+--- a/src/dns.h
++++ b/src/dns.h
+@@ -27,7 +27,7 @@
+ #include <config.h>
+ #include <arpa/inet.h>
+ #include <sys/socket.h>
+-#include <net/if.h>
++#include <linux/if.h>
+ #include <sys/types.h>
+ #include <inttypes.h>
+ #include "rr_types.h"