strongswan: backport upstream MUSL fix for farp_spoofer.c

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

net/strongswan/patches/0002-farp_spoofer-Fix-build-with-musl-C-library.patch

@@ -0,0 +1,37 @@
+commit 540881627fe8083207f9a2cfd01b931164c7ef4e
+Author: Tobias Brunner <tobias@strongswan.org>
+Date:   Fri Mar 22 10:42:34 2024 +0100
+
+    farp: Fix build with musl C library
+    
+    Same issue as described in the previous commit.
+    
+    Fixes: 187c72d1afdc ("dhcp: Port the plugin to FreeBSD/macOS")
+
+--- a/src/libcharon/plugins/farp/farp_spoofer.c
++++ b/src/libcharon/plugins/farp/farp_spoofer.c
+@@ -20,12 +20,14 @@
+ 
+ #include <errno.h>
+ #include <unistd.h>
++#include <net/ethernet.h>
+ #include <sys/ioctl.h>
+ 
+ #if !defined(__APPLE__) && !defined(__FreeBSD__)
+ #include <sys/socket.h>
+-#include <linux/if_arp.h>
+-#include <linux/if_ether.h>
++#include <net/if_arp.h>
++#include <netinet/if_ether.h>
++#include <netpacket/packet.h>
+ #include <linux/filter.h>
+ #else
+ #include <net/bpf.h>
+@@ -33,7 +35,6 @@
+ #include <net/if_dl.h>
+ #endif /* !defined(__APPLE__) && !defined(__FreeBSD__) */
+ 
+-#include <net/ethernet.h>
+ #include <daemon.h>
+ #include <threading/thread.h>
+ #include <processing/jobs/callback_job.h>