Fix ArgumentNullException when Generating without docs -NoDocs switch

[georgend]

Currently the code path below, throws ArgumentNullException when Export-ProxyCmdlet is invoked in the -NoDocs code path.

autorest.powershell/powershell/resources/assets/build-module.ps1

Lines 123 to 134 in f9b8e88

	if($NoDocs) {
	Write-Host -ForegroundColor Green 'Creating exports...'
	Export-ProxyCmdlet -ModuleName $moduleName -ModulePath $modulePaths -ExportsFolder $exportsFolder -InternalFolder $internalFolder -ExcludeDocs
	} else {
	Write-Host -ForegroundColor Green 'Creating exports and docs...'
	$moduleDescription = '${$project.metadata.description}'
	$docsFolder = Join-Path $PSScriptRoot '${$lib.path.relative($project.baseFolder, $project.docsFolder)}'
	if(Test-Path $docsFolder) {
	$null = Get-ChildItem -Path $docsFolder -Recurse -Exclude 'readme.md' | Remove-Item -Recurse -ErrorAction SilentlyContinue
	}
	$null = New-Item -ItemType Directory -Force -Path $docsFolder
	Export-ProxyCmdlet -ModuleName $moduleName -ModulePath $modulePaths -ExportsFolder $exportsFolder -InternalFolder $internalFolder -ModuleDescription $moduleDescription -DocsFolder $docsFolder -ExamplesFolder $examplesFolder -ModuleGuid $guid

Exception is thrown here at Path.Combine, since ExamplesFolder will be null.

autorest.powershell/powershell/resources/psruntime/BuildTime/Cmdlets/ExportProxyCmdlet.cs

Line 76 in 6390998

var examplesFolder = isValidProfile ? Path.Combine(ExamplesFolder, variantGroup.ProfileName) : ExamplesFolder;

Solution
Allow ExamplesFolder to be passed along for all param sets, since examples are already always generated. (Example Stubs).

autorest.powershell/powershell/resources/psruntime/BuildTime/Cmdlets/ExportProxyCmdlet.cs

Lines 45 to 47 in 6390998

	[Parameter(Mandatory = true, ParameterSetName = "Docs")]
	[ValidateNotNullOrEmpty]
	public string ExamplesFolder { get; set; }

Pass along -ExamplesFolder since its required in all code paths.

[dolauli]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[dolauli]

Looks good