Instead of using <build_number>, version build artefacts using git tags. Maintain history and remove dependency on your CI server.

git_version.sh

#!/bin/bash
set -e

SCRIPT=$0
ARG=$1

BASE_VERSION="0.1"

validation_error() {
  echo "Not inside a git repo. Exiting."
  exit 1
}

usage() {
  echo -n " ${SCRIPT} [OPTIONS]

  Versions application using git tags

  Options:

  -b|--bump     Increment the app version
  -p|--publish  Commit the version tag to git repo
  "
  exit 1
}

bump() {
  echo "Current base version is ${BASE_VERSION}"

  PATCH_NUMBER=$(git tag -l "${BASE_VERSION}.*" | wc -l)

  NEXT_VERSION="${BASE_VERSION}.${PATCH_NUMBER}"

  echo "Next app version would be ${NEXT_VERSION}"

  git tag $NEXT_VERSION
}

publish() {
  echo "Checkout and clean any changes to repo"
  git checkout .

  echo "Commit version to the repo"
  git push --tags
}

[[ -d .git ]] || validation_error

case $ARG in
  -b|--bump)
    bump
    ;;
  -p|--publish)
    publish
    ;;
  *)
    usage
    ;;
esac