Refactor Pester installation step in workflow

.github/workflows/build-tool-packages.yml

@@ -160,9 +160,13 @@ jobs:
         Write-Host "to determine if ${{ inputs.tool-name }} version was consumed from cache or if it was downloaded"
         for ($i = 0; $i -lt 200; $i++) { Get-Random }
 
-    - name: Install Pester
+    - name: Ensure Pester Installed
-      run: Install-Module Pester -Force -Scope CurrentUser -SkipPublisherCheck
+      run: |
-
+        $module = Get-Module -ListAvailable -Name Pester
+        if (-not $module -or ($module.Version -lt [Version]"5.0.0")) {
+          Install-Module Pester -Force -Scope CurrentUser -SkipPublisherCheck
+        }
+        
     - name: Run tests
       if: env.excludewinarm == 'true'
       env: