build.sh: Introduce conditional REPO_GROUPS variable to dynamically manage repo groups.

Description

build.sh: Introduce conditional REPO_GROUPS variable to dynamically manage repo groups.

Issue(s)

https://gitlab.e.foundation/e/os/backlog/-/issues/2501

Test procedures

• It should now sync Muppets vendor specific to the target device.
• Android 14 builds should pass without any issues.
• This change will not effect any builds for Android versions below Android 14.

Test Builds

v1-t: https://gitlab.e.foundation/e/priv/os/build/-/jobs/1006162

v1-u: https://gitlab.e.foundation/e/priv/os/build/-/jobs/1006163

Check list

• Self review
• Test procedure explained
• Tested on fresh install
• Tested applied as an update
• License
• Internal documentation
• User documentation