Workaround for accessing Az Artifacts (#8188)

Added a workaround for accessing Az Artifacts feed from release build. 
  - Also, converted the `sh` task to PowerShell.

tools/releaseBuild/macOS/vsts.yml

@@ -23,6 +23,7 @@ steps:
        throw "nuget.config is not created"
    }
   displayName: 'Add nuget.config for AzDevOps feed for PSGallery modules '
+  condition: ne(Variable['SkipFxDependent'], 'true')
 - task: ShellScript@2
   inputs:
     scriptPath: 'tools/installpsh-osx.sh'
@@ -36,10 +37,8 @@ steps:
     scriptPath: 'tools/releaseBuild/macOS/PowerShellPackageVsts.sh'
     args: '-location $(Build.SourcesDirectory) -BootStrap'
   displayName: 'Bootstrap VM'
-- task: ShellScript@2
-  inputs:
-    scriptPath: 'tools/releaseBuild/macOS/PowerShellPackageVsts.sh'
-    args: '-ReleaseTag $(ReleaseTagVar) -Destination $(System.ArtifactsDirectory) -ExtraPackage "tar" -location $(Build.SourcesDirectory) -Build'
-    disableAutoCwd: true
-    cwd: 'tools/releaseBuild/macOS'
+- powershell: |
+    $env:AZDEVOPSFEEDPAT = '$(AzDevOpsFeedPAT)'
+    .\PowerShellPackageVsts.ps1 -ReleaseTag $(ReleaseTagVar) -Destination $(System.ArtifactsDirectory) -ExtraPackage "tar" -location $(Build.SourcesDirectory) -Build
+    $env:AZDEVOPSFEEDPAT = $null
   displayName: 'Build and Package'