[ fix ] Fix CI for building Agda 2.6.4 with Stack

Author: andy0130tw

.github/workflows/test.yml

@@ -130,7 +130,10 @@ jobs:
       - name: ⏬ Install Agda
         if: ${{ steps.check-agda.outcome == 'failure'}}
         run: |
-          stack install --resolver=lts-24.1 --allow-different-user ${{ matrix.agda }}
+          AGDA_PKGNAME=${{ matrix.agda }}
+          STACK_RESOLVER=$([ "$AGDA_PKGNAME" == "Agda-2.6.4" ] && echo "nightly-2023-10-03
+" || echo "lts-24.1")
+          stack install --resolver=$STACK_RESOLVER --allow-different-user "$AGDA_PKGNAME"
           echo "STACK_LOCAL_BIN=$(stack path --local-bin)" >> "$GITHUB_ENV"
 
       - name: 📦 Move artefacts to ${{ env.DIST }}