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 +1,109 @@
+name: Build and Test AppImage
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+    branches:
+      - main
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Determine Version
+        id: version
+        run: |
+          # Get the most recent tag
+          LATEST_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "v0.0.0")
+          
+          # Check if the latest commit is tagged
+          TAGGED_COMMIT=$(git describe --tags --exact-match 2>/dev/null || echo "notag")
+          
+          if [ "$TAGGED_COMMIT" = "notag" ]; then
+            VERSION="${LATEST_TAG}+"
+            DIST="-git"
+          else
+            VERSION=$LATEST_TAG
+            DIST=""
+          fi
+
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+          echo "DIST=$DIST" >> $GITHUB_ENV
+
+      - name: Build AppImage
+        run: |
+          docker run --rm -v $(pwd):/workspace -w /workspace centos:7 /bin/bash -c "
+            set -x
+
+            # Update repository URLs to use the vault since CentOS 7 has reached EOL
+            sed -i 's|^mirrorlist=|#mirrorlist=|g' /etc/yum.repos.d/CentOS-*.repo
+            sed -i 's|^#baseurl=http://mirror.centos.org/centos/\$releasever|baseurl=http://vault.centos.org/7.9.2009|g' /etc/yum.repos.d/CentOS-*.repo
+            
+            yum clean all
+            yum makecache
+
+            yum install -y epel-release
+            yum install -y gcc make automake autoconf gtk3-devel gettext-devel libtool fuse fuse-libs
+            yum install -y gtk3-devel glib2-devel gettext-devel desktop-file-utils \
+                patchelf wget
+
+            # Download AppImageTool
+            wget https://github.com/AppImage/AppImageKit/releases/download/continuous/appimagetool-x86_64 -O appimagetool
+            chmod +x appimagetool
+
+            # Prepare directories
+            mkdir -p AppDir/usr/bin
+            mkdir -p AppDir/usr/share/icons/hicolor/scalable/apps
+            mkdir -p AppDir/usr/share/applications
+
+            # Run autogen.sh and build
+            ./autogen.sh
+            ./configure
+            make
+
+            # Install to AppDir
+            make install DESTDIR=$(pwd)/AppDir
+
+            # Copy additional resources
+            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/
+
+            # Add AppRun script
+            echo '#!/bin/bash' > AppDir/AppRun
+            echo 'exec /usr/bin/xnec2c "$@"' >> AppDir/AppRun
+            chmod +x AppDir/AppRun
+
+            # Create AppImage
+            ./appimagetool AppDir xnec2c-v${VERSION}${DIST}.AppImage
+
+            ls -latr
+
+            # Verify creation and permissions
+            ls -l xnec2c-v${VERSION}${DIST}.AppImage
+            chmod +x xnec2c-v${VERSION}${DIST}.AppImage
+            mv xnec2c-v${VERSION}${DIST}.AppImage xnec2c-${VERSION}${DIST}.AppImage
+          "
+
+      - name: Test AppImage
+        run: |
+          chmod +x xnec2c-${VERSION}${DIST}.AppImage
+          ./xnec2c-${VERSION}${DIST}.AppImage -h
+
+      - name: Upload AppImage
+        uses: actions/upload-artifact@v2
+        with:
+          name: xnec2c-appimage
+          path: xnec2c-${VERSION}${DIST}.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-24.04", "ubuntu-22.04", "ubuntu-20.04", "ubuntu-18.04", "debian-11", "debian-10", "debian-9"]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0  # Fetch full Git history and tags
+
+      - name: Set up the build environment
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential autoconf automake libtool \
+              libgtk-3-dev libglib2.0-dev gettext desktop-file-utils devscripts fakeroot lintian autopoint dh-make dh-autoreconf
+
+      - name: Determine version and dist
+        id: version
+        run: |
+          LATEST_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "0.0.0")
+          TAGGED_COMMIT=$(git describe --tags --exact-match 2>/dev/null || echo "notag")
+          
+          if [ "$TAGGED_COMMIT" = "notag" ]; then
+            VERSION="${LATEST_TAG}+"
+            DIST="-git"
+          else
+            VERSION=$LATEST_TAG
+            DIST=""
+          fi
+
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+          echo "DIST=$DIST" >> $GITHUB_ENV
+
+      - name: Generate Debian Packaging Files
+        run: |
+          if [ ! -d "debian" ]; then
+            dh_make --createorig -y --single --native --packagename xnec2c_$VERSION
+            echo -e '#!/usr/bin/make -f\n%:\n\tdh $@' > debian/rules
+            chmod +x debian/rules
+            echo "9" > debian/compat
+            echo "xnec2c ($VERSION) unstable; urgency=low\n\n  * Initial release.\n\n -- Your Name <[email protected]>  $(date -R)" > debian/changelog
+            cat > debian/control <<EOL
+Source: xnec2c
+Section: utils
+Priority: optional
+Maintainer: Your Name <[email protected]>
+Build-Depends: debhelper (>= 9), autotools-dev, automake, autoconf, libtool, libgtk-3-dev, libglib2.0-dev, gettext, desktop-file-utils
+Standards-Version: 3.9.6
+Homepage: https://www.example.com
+
+Package: xnec2c
+Architecture: any
+Depends: \${shlibs:Depends}, \${misc:Depends}
+Description: A multi-threaded EM tool to model antenna near- and far-field radiation patterns.
+ Xnec2c is a high-performance multi-threaded electromagnetic simulation
+ package to model antenna near- and far-field radiation patterns for
+ Linux and UNIX operating systems.
+EOL
+          fi
+
+      - name: Build the DEB package using debuild
+        run: |
+          ./autogen.sh
+          ./configure
+          make
+          debuild -us -uc -b
+
+      - name: Test DEB package
+        run: |
+          dpkg -i ../xnec2c_*.deb || true
+          xnec2c -h
+
+      - name: Upload the DEB package
+        uses: actions/upload-artifact@v2
+        with:
+          name: xnec2c-${{ matrix.os }}.deb
+          path: ../xnec2c_*.deb

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

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+name: Build RPM Package
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+    branches:
+      - main
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Determine Version
+        id: version
+        run: |
+          # Get the most recent tag
+          LATEST_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "v0.0.0")
+          
+          # Check if the latest commit is tagged
+          TAGGED_COMMIT=$(git describe --tags --exact-match 2>/dev/null || echo "notag")
+          
+          if [ "$TAGGED_COMMIT" = "notag" ]; then
+            VERSION="${LATEST_TAG}+"
+            DIST="-git"
+          else
+            VERSION=$LATEST_TAG
+            DIST=""
+          fi
+
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+          echo "DIST=$DIST" >> $GITHUB_ENV
+
+      - name: Build RPM
+        run: |
+          docker run --rm -v $(pwd):/workspace -w /workspace almalinux:9 /bin/bash -c "
+            set -x
+
+            # Install dependencies
+            dnf install -y epel-release
+            dnf install -y gcc make automake autoconf gtk3-devel gettext-devel libtool \
+                rpm-build rpmdevtools git
+
+            # Prepare the RPM build environment
+            rpmdev-setuptree
+
+            # Generate the spec file
+            ./autogen.sh
+
+            # Build the RPM
+            rpmbuild -ba --define \"_version ${VERSION}\" --define \"_dist ${DIST}\" \
+                --define \"_topdir /root/rpmbuild\" xnec2c.spec
+
+            # Check the RPM files
+            ls -l /root/rpmbuild/RPMS/x86_64
+          "
+
+      - name: Install and Test RPM
+        run: |
+          docker run --rm -v $(pwd):/workspace -w /workspace almalinux:9 /bin/bash -c "
+            # Install the RPM package
+            dnf install -y /root/rpmbuild/RPMS/x86_64/xnec2c-*.rpm
+
+            # Run the test to verify the package
+            xnec2c -h
+          "
+
+      - name: Upload RPM
+        uses: actions/upload-artifact@v2
+        with:
+          name: xnec2c-rpm
+          path: /root/rpmbuild/RPMS/x86_64/xnec2c-*.rpm