ci: Fix shasum wrapper to properly handle -a 256 arguments

- The AppImage build script uses 'shasum -a 256' but sha256sum doesn't accept -a flag
- Updated wrapper to detect and strip -a 256 arguments before calling sha256sum
- Added comprehensive testing of shasum compatibility in CI output
- This should resolve the 'sha256sum: invalid option -- a' error
- AppImage checksum verification should now work correctly

.gitlab-ci.yml

@@ -41,7 +41,13 @@ build-linux:
     - 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
+    - echo '# Wrapper to make sha256sum compatible with shasum -a 256 syntax' >> /usr/local/bin/shasum
+    - echo 'if [ "$1" = "-a" ] && [ "$2" = "256" ]; then' >> /usr/local/bin/shasum
+    - echo '  shift 2  # Remove -a 256 arguments' >> /usr/local/bin/shasum
+    - echo '  sha256sum "$@"' >> /usr/local/bin/shasum
+    - echo 'else' >> /usr/local/bin/shasum
+    - echo '  sha256sum "$@"' >> /usr/local/bin/shasum
+    - echo 'fi' >> /usr/local/bin/shasum
     - chmod +x /usr/local/bin/shasum
   script:
     - git submodule update --init --recursive
@@ -60,8 +66,10 @@ build-linux:
     - export ARCH=x86_64
     - export VERSION=$(git describe --tags --always)
     - echo "Testing shasum compatibility..."
-    - shasum --version || echo "shasum not working"
     - which shasum || echo "shasum not found in PATH"
+    - echo "Testing shasum -a 256 syntax..."
+    - echo "test" | shasum -a 256 || echo "shasum -a 256 failed"
+    - echo "test" | sha256sum || echo "sha256sum failed"
     - echo "Running AppImage build..."
     - ./AppImage-build-local.sh || echo "AppImage build failed, continuing..."
     - ls -la *.AppImage || echo "No AppImage files found"