您不能在单引号或三单引号中插入变量。使用三重双引号:
stdoutpowershell = powershell returnStdout: true, script: """ write-output "Server is $envserverName" """

您不能在单引号或三单引号中插入变量。使用三重双引号:
stdoutpowershell = powershell returnStdout: true, script: """ write-output "Server is $envserverName" """