Fix rustup toolchain and zstd dependency issues

- Add rustup default stable in build step for proper toolchain setup
- Install libzstd-dev for zstd-sys crate compatibility
- Fix rustup toolchain context issues in main workflow
- Add missing zstd development libraries to both workflows
- Ensure all Rust crate dependencies are available

.forgejo/workflows/build-packages.yml

@@ -149,7 +149,8 @@ jobs:
                          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 \
-                         docbook-xml docbook-xsl xsltproc gjs libglib2.0-doc
+                         docbook-xml docbook-xsl xsltproc gjs libglib2.0-doc \
+                         libzstd-dev
 
       - name: Clone bootc source
         run: |
@@ -194,8 +195,9 @@ jobs:
         run: |
           cd bootc-${BOOTC_VERSION}
           echo "Building bootc package with libostree compatibility patch..."
-          # Source Rust environment for the build
+          # Source Rust environment and ensure default toolchain is set
           . ~/.cargo/env
+          rustup default stable
           dpkg-buildpackage -us -uc -b
 
       - name: List built packages