How to let local package installed firstly when build openwrt image?

I'm using the Openwrt Image builder to build the openwrt image.
I have built some packages local and put the pacakages under the 'packages' folder.
I want to install these packages firstly instead of remote downloading.
such as make image PROFILE=Generic PACKAGES="libblobmsg-json"
but I noticed that it always try to download from remote.
Do you have any idea? thank you! I have tried the line 'imagebuilder' to the top, the result is the same.

cat repositories.conf
## Place your custom repositories here, they must match the architecture and version.
# src/gz %n
#src custom file:///tools/thirdparty/sdk/openwrt-imagebuilder-19.07.5-x86-generic.Linux-x86_64/local/

#src imagebuilder file:packages
#src imagebuilder file:packages
## Remote package repositories
src/gz openwrt_core
src/gz openwrt_base
src/gz openwrt_freifunk
src/gz openwrt_luci
src/gz openwrt_packages
src/gz openwrt_routing
src/gz openwrt_telephony

## This is the local package repository, do not remove!
src imagebuilder file:packages