unix: add WireGuard generic netlink interface constants on Linux

Change-Id: I619c49f745da8cfd17bc2aae28d97aff73daf4d5
Reviewed-on: https://go-review.googlesource.com/c/sys/+/371674
Trust: Matt Layher <mdlayher@gmail.com>
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/mkerrors.sh

@@ -261,6 +261,7 @@ struct ltchars {
 #include <linux/vm_sockets.h>
 #include <linux/wait.h>
 #include <linux/watchdog.h>
+#include <linux/wireguard.h>
 
 #include <mtd/ubi-user.h>
 #include <mtd/mtd-user.h>
@@ -606,6 +607,7 @@ ccflags="$@"
 		$2 ~ /^MTD/ ||
 		$2 ~ /^OTP/ ||
 		$2 ~ /^MEM/ ||
+		$2 ~ /^WG/ ||
 		$2 ~ /^BLK[A-Z]*(GET$|SET$|BUF$|PART$|SIZE)/ {printf("\t%s = C.%s\n", $2, $2)}
 		$2 ~ /^__WCOREFLAG$/ {next}
 		$2 ~ /^__W[A-Z0-9]+$/ {printf("\t%s = C.%s\n", substr($2,3), $2)}