Add CI workflows for DEB, RPM, and AppImage builds

- Added `build-deb-packages.yml` to automate the creation of DEB
  packages using `debuild` for all supported Ubuntu and Debian versions.

- Added `build-rpm-packages.yml` to automate the creation of RPM
  packages using `rpmbuild` for all supported Fedora and AlmaLinux
  versions.

- Added `build-appimage.yml` to build an AppImage on CentOS 7, ensuring
  compatibility with systems using `glibc <= 2.17`.

Each workflow includes automated tests and artifact uploads, improving
the packaging and distribution process across multiple Linux
distributions.

.github/workflows/build-appimage.yml

@@ -0,0 +1,48 @@
+name: Build AppImage
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+    branches:
+      - main
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Set up CentOS 7 Docker
+        run: |
+          docker run --rm -v $(pwd):/workspace -w /workspace centos:7 /bin/bash -c "
+            yum install -y epel-release
+            yum groupinstall -y 'Development Tools'
+            yum install -y gtk3-devel glib2-devel gettext-devel desktop-file-utils \
+                patchelf wget libtool autoconf automake pkgconfig
+
+            wget https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage
+            chmod +x linuxdeploy-x86_64.AppImage
+
+            ./autogen.sh
+            ./configure
+            make
+
+            ./linuxdeploy-x86_64.AppImage --appdir AppDir --init-appdir
+            cp src/xnec2c AppDir/usr/bin/
+            cp resources/xnec2c.svg AppDir/usr/share/icons/hicolor/scalable/apps/
+            cp files/xnec2c.desktop AppDir/usr/share/applications/
+            ./linuxdeploy-x86_64.AppImage --appdir AppDir --output appimage
+            mv *.AppImage xnec2c-${{ github.sha }}.AppImage
+
+            chmod +x xnec2c-${{ github.sha }}.AppImage
+            ./xnec2c-${{ github.sha }}.AppImage --appimage-extract-and-run -h
+            "
+
+      - name: Upload the AppImage
+        uses: actions/upload-artifact@v2
+        with:
+          name: xnec2c.AppImage
+          path: xnec2c-${{ github.sha }}.AppImage

.github/workflows/build-deb-packages.yml

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+name: Build DEB Packages
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+    branches:
+      - main
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ubuntu-22.04, ubuntu-20.04, ubuntu-18.04, debian-11, debian-10, debian-9]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up the build environment
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential autoconf automake libtool \
+              gtk3-dev libglib2.0-dev gettext desktop-file-utils devscripts fakeroot lintian
+
+      - name: Build the DEB package using debuild
+        run: |
+          ./autogen.sh
+          ./configure
+          make
+          debuild -us -uc -b
+
+      - name: Test DEB package
+        run: |
+          dpkg -i ../xnec2c_*.deb || true  # Install DEB package
+          xnec2c -h  # Run test
+
+      - name: Upload the DEB package
+        uses: actions/upload-artifact@v2
+        with:
+          name: xnec2c-${{ matrix.os }}.deb
+          path: ../xnec2c_*.deb

.github/workflows/build-rpm-packages.yml

@@ -0,0 +1,74 @@
+name: Build RPM Packages
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+    branches:
+      - main
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [fedora-38, fedora-37, almalinux-9, almalinux-8]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Cache dnf packages
+        uses: actions/cache@v2
+        with:
+          path: /var/cache/dnf
+          key: ${{ runner.os }}-dnf-${{ hashFiles('**/Dockerfile') }}
+          restore-keys: |
+            ${{ runner.os }}-dnf-
+
+      - name: Determine version and dist
+        id: version
+        run: |
+          VERSION=$(git describe --tags --abbrev=0 2>/dev/null || echo "0.0.0")
+          TAG=$(git describe --tags --exact-match 2>/dev/null || echo "notag")
+          if [ "$TAG" = "notag" ]; then
+            DIST="-git"
+          else
+            DIST=""
+          fi
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+          echo "DIST=$DIST" >> $GITHUB_ENV
+
+      - name: Build RPM packages in Docker
+        run: |
+          docker run --rm -v $(pwd):/workspace -w /workspace ${{ matrix.os }} /bin/bash -c "
+            sudo dnf install -y rpm-build make autoconf automake libtool gcc gettext-devel gtk3-devel desktop-file-utils glib2-devel intltool
+            ./autogen.sh
+            ./configure
+            make
+            mkdir -p ~/rpmbuild/SOURCES ~/rpmbuild/SPECS
+            mv . ~/rpmbuild/SOURCES/xnec2c-v${VERSION}
+            tar -czvf ~/rpmbuild/SOURCES/xnec2c-v${VERSION}.tar.gz -C ~/rpmbuild/SOURCES xnec2c-v${VERSION}
+            rpmbuild -ba -D \"_topdir $(pwd)/rpmbuild\" -D \"dist $DIST\" ~/rpmbuild/SPECS/xnec2c.spec
+            cp ~/rpmbuild/RPMS/x86_64/xnec2c-*.rpm ."
+
+      - name: Test RPM Package
+        run: |
+          docker run --rm -v $(pwd):/workspace -w /workspace ${{ matrix.os }} /bin/bash -c "
+            sudo dnf install -y ./xnec2c-*.rpm
+            xnec2c -h"
+
+      - name: Upload the RPM package
+        uses: actions/upload-artifact@v2
+        with:
+          name: xnec2c-${{ matrix.os }}.rpm
+          path: xnec2c-*.rpm