Exit 1 when illegal option rather than do install

Signed-off-by: H Dub <14808878+hdub-tech@users.noreply.github.com>

Author: hdub-tech

install.sh

@@ -126,6 +126,7 @@ while [ $# -gt 0 ]; do
 			;;
 		--*)
 			echo "Illegal option $1"
+			exit 1
 			;;
 	esac
 	shift $(( $# > 0 ? 1 : 0 ))