Add RODC location test

Setup/SetupAssist/.gitignore

@@ -1,2 +1,3 @@
 *.config
 *.txt
+*.log

Setup/SetupAssist/Checks/Test-ReadOnlyDomainControllerLocation.ps1

@@ -0,0 +1,23 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+Function Test-ReadOnlyDomainControllerLocation {
+    $forest = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest()
+    foreach ($domain in $forest.Domains) {
+        foreach ($dc in $domain.DomainControllers) {
+            $cn = $dc.Name.Substring(0, $dc.Name.IndexOf("."))
+            $filter = "(&(objectClass=computer)(cn=$cn))"
+            $searcher = New-Object System.DirectoryServices.DirectorySearcher
+            $searcher.Filter = $filter
+            foreach ($result in $searcher.FindAll()) {
+                if ($result.Properties["primaryGroupID"][0] -eq 521) {
+                    $dn = $result.Properties["distinguishedName"][0].ToString()
+                    if (-not $dn.StartsWith("CN=$cn,OU=Domain Controllers,DC=")) {
+                        ("Domain Controller $cn appears to be in a container other than Domain Controllers. " +
+                            "This will cause /PrepareAd to fail in some scenarios. Please see https://support.microsoft.com/help/5005319 for details.") | Receive-Output -IsWarning
+                    }
+                }
+            }
+        }
+    }
+}

Setup/SetupAssist/SetupAssist.ps1

@@ -16,6 +16,7 @@ param(
 . .\Checks\Test-CriticalService.ps1
 . .\Checks\Test-ExchangeAdLevel.ps1
 . .\Checks\Test-ComputersContainerExists.ps1
+. .\Checks\Test-ReadOnlyDomainControllerLocation.ps1
 . .\Checks\Test-MissingDirectory.ps1
 . .\Checks\Test-MissingMsiFiles.ps1
 . .\Checks\Test-OtherWellKnownObjects.ps1
@@ -126,6 +127,7 @@ Function MainUse {
     Test-MissingDirectory
     Test-ExchangeAdSetupObjects
     Test-ComputersContainerExists
+    Test-ReadOnlyDomainControllerLocation
     Confirm-VirtualDirectoryConfiguration
 
     $exSetupLog = "$($env:HOMEDRIVE)\ExchangeSetupLogs\ExchangeSetup.log"