ci: Update apt before attempting install

Author: tommy-gilligan

.github/workflows/ci.yml

@@ -39,6 +39,8 @@ jobs:
 
       - name: Install armv7 libraries
         if: ${{ matrix.target == 'armv7-unknown-linux-gnueabihf' }}
-        run: sudo apt-get install -y libc6-armhf-cross libc6-dev-armhf-cross gcc-arm-linux-gnueabihf
+        run: |
+            sudo apt-get update
+            sudo apt-get install -y libc6-armhf-cross libc6-dev-armhf-cross gcc-arm-linux-gnueabihf
 
       - run: cargo check --target=${{ matrix.target }} --features=${{ matrix.features }}