print message during build for currently not supported machine types

Author: sholzmayer

build

@@ -5,4 +5,6 @@ if [ ${MACHINE_TYPE} == 'x86_64' ]; then
   docker build -t networkboot/dhcpd "$@" $(dirname $0)
 elif [ ${MACHINE_TYPE} == 'armv7l' ]; then
   docker build -t networkboot/dhcpd:arm32v7 "$@" $(dirname $0) -f Dockerfile.arm32v7
+else 
+  echo "Your machine type $MACHINE_TYPE is currently not supported" >&2
 fi