Fix devkitPro install by setting up apt repo manually

The installer script exits with code 8 on Ubuntu. Replace with manual
GPG key + apt source setup followed by apt-get install devkitpro-pacman.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -21,10 +21,15 @@ runs:
     - name: Install devkitPro pacman
       shell: bash
       run: |
-        wget -q https://apt.devkitpro.org/install-devkitpro-pacman \
-          -O /tmp/install-devkitpro-pacman
-        chmod +x /tmp/install-devkitpro-pacman
-        sudo /tmp/install-devkitpro-pacman
+        wget -q https://apt.devkitpro.org/devkitpro-pacman.asc \
+          -O /tmp/devkitpro-pacman.asc
+        sudo mkdir -p /usr/share/keyrings
+        sudo mv /tmp/devkitpro-pacman.asc /usr/share/keyrings/devkitpro-pub.gpg
+        echo "deb [signed-by=/usr/share/keyrings/devkitpro-pub.gpg] https://apt.devkitpro.org stable main" \
+          | sudo tee /etc/apt/sources.list.d/devkitpro.list
+        sudo apt-get update
+        sudo apt-get install -y devkitpro-pacman
+        sudo dkp-pacman -Sy
         echo "DEVKITPRO=/opt/devkitpro" >> $GITHUB_ENV
         echo "DEVKITPPC=/opt/devkitpro/devkitPPC" >> $GITHUB_ENV
         echo "/opt/devkitpro/tools/bin" >> $GITHUB_PATH