Dockerimage not being built: missing git

[jolly-jump]

Describe the bug I try to build my own image from the v2 branch, either like described here: https://docs.bigbluebutton.org/greenlight/gl-customize.html or using "docker build" directly in the git repo.

To Reproduce

• clone repo
• switch to v2 branch
• try to build image using "./scripts/image_build.sh test/greenlight release-2.12.6"

Expected behavior Well, it should compile.

Actual behavior Does not compile, since at least 2.12.1. These are the error messages:

Step 13/34 : RUN bundle config --global frozen 1     && bundle config set deployment 'true'     && bundle config set without 'development:test:assets'     && bundle install -j4 --path=vendor/bundle
 ---> Running in eb61aaf5d24e
`/root` is not writable.
Bundler will use `/tmp/bundler20220704-6-1d9zfku6' as your home directory temporarily.
`/root` is not writable.
Bundler will use `/tmp/bundler20220704-7-x6xlex7' as your home directory temporarily.
`/root` is not writable.
Bundler will use `/tmp/bundler20220704-8-1rex8rn8' as your home directory temporarily.
`/root` is not writable.
Bundler will use `/tmp/bundler20220704-1-109kzz1' as your home directory temporarily.
Fetching gem metadata from https://rubygems.org/........
Fetching https://github.com/blindsidenetworks/tabler-rubygem.git
--- ERROR REPORT TEMPLATE -------------------------------------------------------
# Error Report
[...]
Errno::ENOENT: No such file or directory - git
  /usr/local/lib/ruby/2.7.0/open3.rb:213:in `spawn'
  /usr/local/lib/ruby/2.7.0/open3.rb:213:in `popen_run' 

Additional Information:

• git was actually installed in Step 10 of the build process.
• the same error messages /root not being writable come up here as well: #3439