Install CiviCRM without installing the database. And install the database without installing CiviCRM
From the excellent interactive documentation here -- https://buildkit.civicrm.org/#/tutorials (which is almost impossible to find unless you know where to look):

## Download application (with civibuild)
civibuild download "mytestbuild" \
  --civi-ver "master" \
  --type "drupal-clean"


There are a number of interesting gotchas. For example, civibuild download does not download dependencies for civi, it only downloads civi and the CMS. So you may wish to run composer install and npm install between these two stages. Otherwise, both will be run automatically next.

Then install the DB and the rest of the application:

## Install application (with civibuild)
civibuild install "mytestbuild" \
  --url "http://localhost:8000" \
  --admin-pass "n0ts3cr3t"