Instructions for many tools from the Linux world suggest setting an environment variable for a single invocation of a command like:

JEKYLL_ENV=production jekyll build

The equivalent in PowerShell is cumbersome:

try {
    $oldValue = $env:JEKYLL_ENV
    $env:JEKYLL_ENV = "production"
    jekyll build
} finally {
    $env:JEKYLL_ENV = $oldValue
}

I believe a similar syntax could work in PowerShell:

$env:JEKYLL_ENV="production" jekyll build