linux: add constant PACKET_IGNORE_OUTGOING

(cherry picked from commit 29ab31e)
(backport <rust-lang#4319>)

Author: ryancdotorg

libc-test/semver/linux.txt

@@ -2084,6 +2084,7 @@ PACKET_FANOUT_QM
 PACKET_FANOUT_RND
 PACKET_FANOUT_ROLLOVER
 PACKET_HOST
+PACKET_IGNORE_OUTGOING
 PACKET_KERNEL
 PACKET_LOOPBACK
 PACKET_LOSS

src/unix/linux_like/linux/mod.rs

@@ -3840,6 +3840,7 @@ pub const PACKET_LOSS: c_int = 14;
 pub const PACKET_TIMESTAMP: c_int = 17;
 pub const PACKET_FANOUT: c_int = 18;
 pub const PACKET_QDISC_BYPASS: c_int = 20;
+pub const PACKET_IGNORE_OUTGOING: c_int = 23;
 
 pub const PACKET_FANOUT_HASH: c_uint = 0;
 pub const PACKET_FANOUT_LB: c_uint = 1;