gistfile1.ps1

function Set-AvailableAndDefaultPageLayouts 
{
 param (
   [Microsoft.SharePoint.Client.ClientContext]$clientContext,
   [Microsoft.SharePoint.Client.Web]$web,
   [array]$pageLayoutUrls,
   [string]$defaultPageLayoutUrl
 )
 process
 {
    Write-Host "Setting available page layouts and default page layout on " $web.Url -NoNewLine
    
    $allProps = $web.AllProperties
    $serverRelativeSiteUrl = $web.ServerRelativeUrl
    $clientContext.Load($web)
    $clientContext.Load($allProps)
    $clientContext.ExecuteQuery()
    $defaultPageLayoutXml = ""
    $pageLayoutXml = "<pagelayouts>"
    $pageLayoutUrls | % {
    $pageLayoutXml = $pageLayoutXml + "<layout"
    $fileUrl = $_
    $serverRelativeSiteUrl =$clientContext.Site.RootWeb.ServerRelativeUrl
    $file =$clientContext.Site.RootWeb.GetFileByServerRelativeUrl($serverRelativeSiteUrl + $fileUrl)
    $clientContext.Load($file)
    $clientContext.ExecuteQuery()
    $listItemFields = $file.ListItemAllFields
    $clientContext.Load($listItemFields)
    $clientContext.ExecuteQuery()
    $fileUrl = $fileUrl.TrimStart("/")
    
    $pageLayoutXml += " guid=`"" +$listItemFields.FieldValues["UniqueId"] + "`" url=`"" + $fileUrl +"`" />"
    
    if ($_ -eq $defaultPageLayoutUrl) {
             $defaultPageLayoutXml = "<layout guid=`"" +$listItemFields.FieldValues["UniqueId"] + "`" url=`"" + $fileUrl +"`" />"
    }
 }

   $pageLayoutXml += "</pagelayouts>"
   
   if ($pageLayoutXml -ne "<pagelayouts></pagelayouts>") {
      $allProps["__PageLayouts"] = $pageLayoutXml
   }
   
   if ($defaultPageLayoutXml -ne "") {
      $allProps["__DefaultPageLayout"] = $defaultPageLayoutXml
   }
   
   $web.Update()
   $clientContext.ExecuteQuery()
   Write-Host " Done" -ForegroundColor Green
 }
}