unix: add consts for ELF handling

This adds a few constants that help to handle ELF files and coredumps.

Change-Id: Ifd4c1bd4c8839065af4233ccbf42964a8e96fdf8
Reviewed-on: https://go-review.googlesource.com/c/sys/+/713980
Reviewed-by: Tobias Klauser <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Sean Liao <[email protected]>
Auto-Submit: Sean Liao <[email protected]>
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: florianl

unix/mkerrors.sh

@@ -226,6 +226,7 @@ struct ltchars {
 #include <linux/cryptouser.h>
 #include <linux/devlink.h>
 #include <linux/dm-ioctl.h>
+#include <linux/elf.h>
 #include <linux/errqueue.h>
 #include <linux/ethtool_netlink.h>
 #include <linux/falloc.h>
@@ -529,6 +530,7 @@ ccflags="$@"
 		$2 ~ /^O[CNPFPL][A-Z]+[^_][A-Z]+$/ ||
 		$2 ~ /^(NL|CR|TAB|BS|VT|FF)DLY$/ ||
 		$2 ~ /^(NL|CR|TAB|BS|VT|FF)[0-9]$/ ||
+		$2 ~ /^(DT|EI|ELF|EV|NN|NT|PF|SHF|SHN|SHT|STB|STT|VER)_/ ||
 		$2 ~ /^O?XTABS$/ ||
 		$2 ~ /^TC[IO](ON|OFF)$/ ||
 		$2 ~ /^IN_/ ||