Ruby app CMD cannot find bundler

I have a Ruby app based on ruby:2.5.3-alpine with a CMD that cannot find bundler.

It's being built as:

docker-slim build --http-probe --include-shell --include-exe sleep --include-exe grep --include-exe jq --include-exe /usr/local/bin/bundle myapp

CMD:

CMD ["./scripts/server.sh"]

server.sh:

#!/bin/sh

# Starting puma server
bundle exec puma -C config/puma.rb

I'm not sure if --include-exe pointing to bundler's absolute path is correct. I also tried --include-bin without success.

When running docker-compose pointing to my-app.slim, it raises the following error:

my-app | ./scripts/server.sh: line 4: bundle: not found

Client: Docker Engine - Community
 Version:           19.03.4
 API version:       1.40
 Go version:        go1.12.10
 Git commit:        9013bf5
 Built:             Thu Oct 17 23:44:48 2019
 OS/Arch:           darwin/amd64
 Experimental:      false

Let me know if you have any idea. Thanks in advance!

Start by reproducing the docker-slim build command and running the resulting my-app.slim image with the shown CMD. Inspect ./scripts/server.sh and the Ruby image's Bundler setup, then compare the slim image with the original container. Done means the server script can resolve bundle and launch Puma in the slim image.