ci: Fix AppImage build on CachyOS by adding shasum compatibility

- Create shasum wrapper script that uses sha256sum (available on CachyOS)
- Add debugging output to diagnose AppImage build issues
- The AppImage build script expects shasum but CachyOS uses sha256sum
- This should resolve the 'shasum: command not found' error and enable AppImage creation

.gitlab-ci.yml

@@ -39,6 +39,10 @@ build-linux:
     - pacman -S --noconfirm nasm
     - pacman -S --noconfirm glslang
     - pacman -S --noconfirm fuse2 gdb
+    # Create shasum compatibility wrapper for AppImage build
+    - echo '#!/bin/bash' > /usr/local/bin/shasum
+    - echo 'sha256sum "$@"' >> /usr/local/bin/shasum
+    - chmod +x /usr/local/bin/shasum
   script:
     - git submodule update --init --recursive
     - mkdir -p build && cd build
@@ -55,7 +59,12 @@ build-linux:
     - export APPIMAGE_EXTRACT_AND_RUN=1
     - export ARCH=x86_64
     - export VERSION=$(git describe --tags --always)
+    - echo "Testing shasum compatibility..."
+    - shasum --version || echo "shasum not working"
+    - which shasum || echo "shasum not found in PATH"
+    - echo "Running AppImage build..."
     - ./AppImage-build-local.sh || echo "AppImage build failed, continuing..."
+    - ls -la *.AppImage || echo "No AppImage files found"
   artifacts:
     paths:
       - build/bin/citron