[BUG] v7.x npm_config_* flags not being set for boolean values

[MylesBorins]

Current Behavior:

When running npm install --extra-parameter the npm_config_extra_param ENV VAR is not being set.
It does set when passing a string e.g. npm install --extra-parameter=cool, but not when explicitly set to a boolean e.g. npm install --extra-parameter=true or npm install --extra-parameter=1

Expected Behavior:

Running npm install with additional boolean parameter should set the appropriate ENV VAR

Steps To Reproduce:

$ git clone https://github.com/bzoz/omg-i-pass-with-install-param.git
$ cd omg-i-pass-with-install-param
$ npm install --extra-param

The above fails on 7.x and passes on 6.x

Environment:

OS: MacOS 10.15.6
Node: 14.6.0
npm: 7.0.0-beta.2