Ignore -postfix parameter to PackEachExperiment if prerelease tag is not specified

This should hopefully be all we need for our release build

Author: michael-hawker

.github/workflows/build.yml

@@ -165,7 +165,7 @@ jobs:
       # Build All Packages
       - name: pack experiments
         working-directory: ./tooling/Scripts/
-        run: ./PackEachExperiment.ps1 -date ${{ env.VERSION_DATE }} -postfix ${{ env.VERSION_PROPERTY }}
+        run: ./PackEachExperiment.ps1 -date ${{ env.VERSION_DATE }}${{ env.VERSION_PROPERTY != '' && format(' -postfix {0}', env.VERSION_PROPERTY) || '' }}
 
       # Push Pull Request Packages to our DevOps Artifacts Feed (see nuget.config)
       - name: Push Pull Request Packages (if not fork)