build the spec file
gem build gemname.spec
extract gem files to current path
gem unpack
install local gem in console
gem install --local gem_name.gem
set your gem is local
bundle config local.mygem /path/to/mygem
suposing your gem is my-gem.1.0.1.gem
gem 'my-gem', '1.0.1'
delete your local config for local gem
bundle config --delete local.mygem
install local gem in gemfile
gem 'gem_name', 'gem_version', path: './path_of_gem-version'
adding linux compatibility to Gemfile.lock
bundle lock --add-platform x86_64-linux-musl