A equipe do Powershell tem um consertar isso no blog deles .
Conteúdo do script do site mencionado Update-gac.ps1
Set-Alias ngen (Join-Path ([System.Runtime.InteropServices.RuntimeEnvironment]::GetRuntimeDirectory()) ngen.exe)
[AppDomain]::CurrentDomain.GetAssemblies() |
sort {Split-path $_.location -leaf} |
%{
$Name = (Split-Path $_.location -leaf)
if ([System.Runtime.InteropServices.RuntimeEnvironment]::FromGlobalAccessCache($_))
{
Write-Host "Already GACed: $Name"
}else
{
Write-Host -ForegroundColor Yellow "NGENing : $Name"
ngen $_.location | %{"'t$_"}
}
}