ci: add shell to setup action run steps

.github/actions/setup-arch/action.yml

@@ -6,6 +6,7 @@ runs:
   steps:
     - name: Get week
       id: date
+      shell: bash
       run: echo "week=$(date +%Y-%U)" >> $GITHUB_OUTPUT
 
     - name: Cache packages
@@ -18,10 +19,12 @@ runs:
           pacman-
 
     - name: Install deps
+      shell: bash
       run: |
         pacman -Syu --needed --noconfirm sudo base-devel cmake ninja fish git clang qt6-declarative python
 
     - name: Install quickshell-git
+      shell: bash
       run: |
         useradd -m builder
         echo 'builder ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers