To support the eventual migration of the CLI to ESM, the CLI commandline tool is now bootstrapped by dynamically importing the main initialization code. This is done to allow the main bin file (`ng`) to remain CommonJS so that older versions of Node.js can be checked and validated prior to the execution of the CLI. This separate bootstrap file is needed to allow the use of a dynamic import expression without crashing older versions of Node.js that do not support dynamic import expressions and would otherwise throw a syntax error. This bootstrap file is required from the main bin file only after the Node.js version is determined to be in the supported range. The use of the dynamic import expression allows CommonJS code to execute either CommonJS or ESM code.
This postinstall script was put in place during the v6.0 timeframe to aid users migrating from the v1.x configuration file format by displaying a message instructing the user to run `ng update`.
The `ng update` migration is still functional and users can still use it to migrate from a v1.x project. However, the postinstall script will no longer be run for every install of the Angular CLI.
