Fix workflow shell issues and add missing build dependencies

- Use bash shell and POSIX-compliant sourcing
- Add debhelper-compat, dh-cargo, rustc, cargo packages
- Install system Rust before rustup for dpkg compatibility

.forgejo/workflows/build-packages.yml

@@ -39,6 +39,9 @@ jobs:
           apt update -y
           apt install -y git curl pkg-config build-essential gnupg
           
+          # Install system Rust packages first for dpkg-buildpackage compatibility
+          apt install -y rustc cargo
+          
           # Install Rust using rustup to get the latest version
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
           . ~/.cargo/env
@@ -138,7 +141,8 @@ jobs:
       - name: Install additional build dependencies
         run: |
           apt update -y
-          apt install -y libglib2.0-dev libgpgme-dev libssl-dev libcurl4-gnutls-dev \
+          apt install -y debhelper-compat dh-cargo \
+                         libglib2.0-dev libgpgme-dev libssl-dev libcurl4-gnutls-dev \
                          libarchive-dev libfuse3-dev libsystemd-dev libmount-dev \
                          libselinux1-dev libavahi-client-dev libavahi-glib-dev \
                          libsoup-3.0-dev gobject-introspection gtk-doc-tools \