CiviCRM BuildKit install fails on Ubuntu 18.04.1 LTS
Updated:
The fix for this has now been merged as https://github.com/civicrm/civicrm-buildkit/pull/427
Original
Full solution: https://github.com/civicrm/civicrm-buildkit/issues/426
Assuming that we can get this fixed in the BuildKit installer this answer will be updated to reflect such a change.

Install a compatible version of NodeJS/NPM from NodeSource

curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -


Download, don't run, the get-buildkit.sh script.

wget https://civicrm.org/get-buildkit.sh


Using the editor of your choice, edit the downloaded script.

editor get-buildkit.sh


On line 453:

(PACKAGES=&quot;acl git wget unzip zip mysql-server mysql-client php7.2-cli php7.2-imap php7.2-ldap php7.2-curl php7.2-mysql php7.2-intl php7.2-gd php7.2-dev php7.2-bcmath php7.2-mbstring php7.2-soap php7.2-zip php7.2-xml apache2 libapache2-mod-php7.2 nodejs npm php-pear libmcrypt-dev libreadline-dev&quot;)
Remove npm:
(PACKAGES=&quot;acl git wget unzip zip mysql-server mysql-client php7.2-cli php7.2-imap php7.2-ldap php7.2-curl php7.2-mysql php7.2-intl php7.2-gd php7.2-dev php7.2-bcmath php7.2-mbstring php7.2-soap php7.2-zip php7.2-xml apache2 libapache2-mod-php7.2 nodejs php-pear libmcrypt-dev libreadline-dev&quot;)


Make the script executable:

chmod +x get-buildkit.sh


Install BuildKit:
Important The script CANNOT be in the same directory you intend to install BuildKit to!

./get-buildkit.sh --full --dir ~/buildkit


Continue the usual steps from here:

https://docs.civicrm.org/dev/en/latest/tools/buildkit/#config