[ci] Remove old packages before building

.gitlab-ci.yml

@@ -51,8 +51,9 @@ deb-for-buster: &deb-for-buster
     - mk-build-deps -ir -t 'apt-get -y --no-install-recommends'
     - gem install bundler -v 2.1.4
     - apt-get install -y curl pkg-config
-    - dpkg-buildpackage
     - mkdir pkg
+    - rm ../*deb
+    - dpkg-buildpackage
     - cp ../*deb pkg/
   artifacts:
     paths: