ci: tweak the builder so it doesnt regard the packages change

Author: Cammin

.github/workflows/unity-builder.yml

@@ -41,7 +41,10 @@ jobs:
 
             #Use a custom packages list instead of the original manifest
             - name: Use CI Manifest
-              run: cp Packages/manifest_ci.json Packages/manifest.json
+              run: |
+                cp Packages/manifest_ci.json Packages/manifest.json
+            #Make the branch think it's not dirty so the builder still runs
+                git update-index --assume-unchanged Packages/manifest.json
 
             #Build Cache
             - uses: actions/cache@v4.2.3