Use minimal checkout for private repo

Author: chidozieononiwu

eng/pipelines/templates/stages/archetype-spec-gen-sdk.yml

@@ -179,7 +179,14 @@ stages:
           displayName: "Validate and update SDK repository commitish"
 
       - ${{ if and(eq(variables['System.TeamProject'], 'internal'), endsWith(variables['Build.Repository.Name'], '-pr')) }}:
+        - checkout: self
+          displayName: 'Sparse checkout eng/common/scripts for GitHub login'
+          path: s/_login_scripts
+          sparseCheckoutDirectories: eng/common/scripts
+          fetchDepth: 1
         - template: /eng/common/pipelines/templates/steps/login-to-github.yml
+          parameters:
+            ScriptDirectory: $(Pipeline.Workspace)/s/_login_scripts/eng/common/scripts
 
       - template: /eng/common/pipelines/templates/steps/sparse-checkout.yml
         parameters: