chore(skip,ci): make better use of BUILT_DEB_FILE, set RUST_BACKTRACE…

… at build time

- always set BUILT_DEB_FILE to silence a warning
- make better use of BUILT_DEB_FILE
- set RUST_BACKTRACE at build time
- don't upload a deb in release workflow unless the matrix is configured to build one

.github/workflows/ci.yml

@@ -12,7 +12,9 @@ on:
   workflow_dispatch:
 
 env:
+  BUILT_DEB_FILE: "invalid.deb" # updated by make-debian-package script
   CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
 
 jobs:
   # Build the app on all supported platforms, at least for the time being

.github/workflows/release.yml

@@ -6,7 +6,9 @@ on:
   workflow_dispatch: # for testing
 
 env:
+  BUILT_DEB_FILE: "invalid.deb" # updated by make-debian-package script
   CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
 
 permissions:
   contents: write
@@ -71,9 +73,9 @@ jobs:
       uses: actions/upload-artifact@v4
       with:
         name: qcp-deb-${{ matrix.target }}
-        path: target/**/debian/qcp*.deb
+        path: ${{ env.BUILT_DEB_FILE }}
     - name: Publish deb package to release
-      if: ${{ github.event_name == 'release' }}
+      if: ${{ matrix.build_deb }} && ${{ github.event_name == 'release' }}
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: gh release upload ${{ github.ref }} ${{ env.BUILT_DEB_FILE }}