shrc: simplify per-host customization

Use ~/.shrc.local instead of ~/.shrc.$(hostname)

dotfiles/shrc

@@ -77,11 +77,8 @@ if command -v calendar >/dev/null && [ -f ~/.calendar/calendar ]; then
 	calendar
 fi
 
-_host=$(hostname 2>/dev/null)
-_host=${_host%%.*}
-if [ -n "$_host" ] && [ -f ~/.shrc."$_host" ]; then
-	. ~/.shrc."$_host"
+if [ -s ~/.shrc.local ]; then
+	. ~/.shrc.local
 fi
-unset _host
 
 set -o emacs