Update CI workflow to install dependencies for secure AMIs

Due to the switch to more secure AMIs, we now install required packages
as part of the workflow.

This change ensures that all necessary tools and libraries are available
during the build process.

.github/workflows/ci-aarchxx.yml

@@ -51,12 +51,12 @@ jobs:
       matrix:
         # This job will run in parallel.
         include:
-          - os: ubuntu-20-arm64-pre-sve
+          - os: ah-ubuntu_20_04-c6g_4x-50
             sve: false
-          - os: ubuntu-20-arm64-sve
+          - os: ah-ubuntu_20_04-c7g_4x-50
             sve: true
             sve_length: 256
-          - os: ubuntu-20-arm64-sve
+          - os: ah-ubuntu_20_04-c7g_4x-50
             sve: true
             sve_length: 128
     runs-on: ${{ matrix.os }}
@@ -82,6 +82,20 @@ jobs:
       - name: Fetch master
         run: git fetch --no-tags --depth=1 origin master
 
+      - name: Install dependencies
+        run: |
+          sudo apt update >& /dev/null && \
+          sudo DEBIAN_FRONTEND=noninteractive apt install -y --no-install-recommends \
+            build-essential \
+            cmake \
+            doxygen \
+            git \
+            libunwind-dev \
+            openssh-client \
+            python3 \
+            zlib1g-dev \
+            >& /dev/null
+
       - name: Create build directory
         run: mkdir build