ci: simplify aarch64-linux cross-compile (CLI-only, skip UI)

The arm64 multiarch apt setup was failing because the Azure mirror on
GitHub runners only serves amd64. Since we don't build the UI for
aarch64-linux (server target), we only need the cross-compiler itself,
which is amd64-native. Drop the arm64 system libs and the best-effort
UI build step.

Author: therealaleph

.github/workflows/release.yml

@@ -56,21 +56,10 @@ jobs:
       - name: Install aarch64 cross-compile toolchain (Linux only)
         if: matrix.target == 'aarch64-unknown-linux-gnu'
         run: |
-          sudo dpkg --add-architecture arm64
-          sudo sed -i 's#^deb http#deb [arch=amd64] http#' /etc/apt/sources.list || true
-          echo 'deb [arch=arm64] http://ports.ubuntu.com/ubuntu-ports jammy main restricted universe multiverse' | sudo tee /etc/apt/sources.list.d/arm64.list
-          echo 'deb [arch=arm64] http://ports.ubuntu.com/ubuntu-ports jammy-updates main restricted universe multiverse' | sudo tee -a /etc/apt/sources.list.d/arm64.list
           sudo apt-get update
-          sudo apt-get install -y gcc-aarch64-linux-gnu \
-            libxkbcommon-dev:arm64 \
-            libwayland-dev:arm64 \
-            libxcb1-dev:arm64 libxcb-render0-dev:arm64 libxcb-shape0-dev:arm64 libxcb-xfixes0-dev:arm64 \
-            libx11-dev:arm64 \
-            libgl1-mesa-dev:arm64 libglib2.0-dev:arm64 libgtk-3-dev:arm64 || true
+          sudo apt-get install -y gcc-aarch64-linux-gnu
           echo '[target.aarch64-unknown-linux-gnu]' >> ~/.cargo/config.toml
           echo 'linker = "aarch64-linux-gnu-gcc"' >> ~/.cargo/config.toml
-          echo "PKG_CONFIG_PATH=/usr/lib/aarch64-linux-gnu/pkgconfig:/usr/share/pkgconfig" >> $GITHUB_ENV
-          echo "PKG_CONFIG_ALLOW_CROSS=1" >> $GITHUB_ENV
 
       - name: Install Windows MinGW toolchain
         if: matrix.target == 'x86_64-pc-windows-gnu'
@@ -100,11 +89,6 @@ jobs:
         if: matrix.target != 'aarch64-unknown-linux-gnu'
         run: cargo build --release --target ${{ matrix.target }} --features ui --bin mhrv-rs-ui
 
-      - name: Try UI on aarch64-linux (best effort)
-        if: matrix.target == 'aarch64-unknown-linux-gnu'
-        continue-on-error: true
-        run: cargo build --release --target ${{ matrix.target }} --features ui --bin mhrv-rs-ui
-
       - name: Package (unix)
         if: runner.os != 'Windows'
         run: |