Use correct paths in update-etherncodes.sh
Bug: https://bugs.gentoo.org/783195

--- a/update-ethercodes.sh.in
+++ b/update-ethercodes.sh.in
@@ -6,22 +6,19 @@
 
 prog="`basename $0`"
 
-PATH=/usr/local/bin:${PATH}
-export PATH
-
 t1=/tmp/${prog}.1.$$
 
 trap 'rm -f ${t1}; exit 1' 1 2 3 15 EXIT
 
 if [ ! -f arp.dat ]; then
-	cd /usr/local/arpwatch || exit 1
+	cd @datarootdir@/arpwatch || exit 1
 fi
 
 fn=ethercodes.dat
 url=https://standards-oui.ieee.org/oui/oui.csv
 
 cmd1="curl --no-progress-meter ${url}"
-cmd2=./massagevendor
+cmd2=@sbindir@/massagevendor.py
 
 # Emit exit status of first command in pipe
 # https://unix.stackexchange.com/a/70675