Start appveyor build with API and pass value for Environment Variable

StartBuildPassEnvVar.ps1

Param([string]$myVar )

$token = '<API_Token>'

$headers = @{
  "Authorization" = "Bearer $token"
  "Content-type" = "application/json"
}

$body = @{
    accountName="<Your_account>"
    projectSlug="<Your_project_slug>"
    branch="<Your_branch>"    
    environmentVariables = @{
       my_var=$myVar 
    }    
}
$body = $body | ConvertTo-Json

Invoke-RestMethod -Uri 'https://ci.appveyor.com/api/builds' -Headers $headers  -Body $body -Method POST