ci: Fix YAML by installing real shasum instead of wrapper

- Reverted to last working commit 72353c75 (successful AppImage creation)
- Replace heredoc shasum wrapper with simple perl-digest-sha installation
- This provides the real shasum command without YAML parsing issues
- Minimal change to proven working configuration
- Should maintain all functionality while fixing YAML validation

.gitlab-ci.yml

@@ -39,19 +39,8 @@ build-linux:
     - pacman -S --noconfirm nasm
     - pacman -S --noconfirm glslang
     - pacman -S --noconfirm fuse2 gdb
-    # Create shasum compatibility wrapper for AppImage build
-    - |
-      cat > /usr/local/bin/shasum << 'EOF'
-      #!/bin/bash
-      # Wrapper to make sha256sum compatible with shasum -a 256 syntax
-      if [ "$1" = "-a" ] && [ "$2" = "256" ]; then
-        shift 2
-        sha256sum "$@"
-      else
-        sha256sum "$@"
-      fi
-      EOF
-    - chmod +x /usr/local/bin/shasum
+    # Install shasum for AppImage compatibility  
+    - pacman -S --noconfirm perl-digest-sha
   script:
     - git submodule update --init --recursive
     - mkdir -p build && cd build