Prevent running CI on forks

Incorporates the changes from https://github.com/zeldaret/oot/pull/2788

.github/workflows/ci.yml

@@ -9,6 +9,8 @@ jobs:
   build_repo:
     # This is a *private* build container.
     container: ghcr.io/zeldaret/mm-build:main
+    # Prevent running outside zeldaret/mm as fetching the container would fail anyway.
+    if: ${{ github.repository == 'zeldaret/mm' }}
 
     name: Build repo (${{ matrix.version }})
     runs-on: ubuntu-latest
@@ -120,7 +122,7 @@ jobs:
     needs: [build_repo]
     runs-on: ubuntu-latest
     # Solution 1 from https://github.com/actions/runner/issues/2566#issuecomment-3053484216
-    if: always()
+    if: 'always() && ${{ github.repository == ''zeldaret/mm'' }}'
     steps:
       - run: |
          if [ "${{ needs.build_repo.result }}" != "success" ]; then
@@ -131,7 +133,7 @@ jobs:
     name: Merge BSS fixes
     runs-on: ubuntu-latest
     needs: [build_repo]
-    if: '!cancelled()'  # Run even if build_repo fails
+    if: '!cancelled() && ${{ github.repository == ''zeldaret/mm'' }}'  # Run even if build_repo fails
     steps:
       - name: Checkout repository
         uses: actions/checkout@v6