build: add GitHub workflows on real GitHub

There is a difference between act-cli and real GitHub environment:
without git executable inside the container, checkout action downloads
a tarball. It seems that binary files are missing in that tarball and
therefore AppImage build fails due to missing icon file.

- add ca-certificates & git packages to dependencies
- move checkout step after dependency installation

.github/workflows/build-linux.yml

@@ -50,13 +50,10 @@ jobs:
 
       - name: Add packages for AppImage Build
         run: |
-          echo "APPIMAGE_PACKAGES=ca-certificates curl file nodejs" >>${GITHUB_ENV}
+          echo "APPIMAGE_PACKAGES=curl file nodejs" >>${GITHUB_ENV}
         if: |
           matrix.appimage
 
-      - name: Checkout
-        uses: actions/checkout@v3
-
       - name: Update for Debian systems
         run: |
           apt-get update -q -y
@@ -67,6 +64,8 @@ jobs:
       - name: Install dependencies for Debian systems
         run: >
           apt-get install --no-install-recommends -q -y
+          ca-certificates
+          git
           cmake
           ninja-build
           g++
@@ -88,6 +87,8 @@ jobs:
       - name: Install dependencies for RedHat systems
         run: >
           dnf install --setopt=install_weak_deps=False -y
+          ca-certificates
+          git
           cmake
           ninja-build
           gcc-c++
@@ -102,8 +103,13 @@ jobs:
         if: |
           env.OS_RELEASE_ID == 'fedora'
 
+      # NOTE: execute *AFTER* dependency installation to ensure that it uses a git checkout!
+      - name: Checkout
+        uses: actions/checkout@v3
+
       - name: Configure
         run: |
+          ls -lhtaR ${{ github.workspace }}/data/icons/
           rm -rf ${{ runner.temp }}/build
           cmake -GNinja -B ${{ runner.temp }}/build .