Fix ubuntu-20.04 CI test

Signed-off-by: falkTX <falktx@falktx.com>

.github/workflows/build.yml

@@ -317,6 +317,7 @@ jobs:
         apt-get source -d jackd2
         tar xf *.debian.tar.xz
         rm -rf debian/source
+        sed -i "s|--prefix=/usr --classic|--prefix=/usr --example-tools --classic|" debian/rules
         dch -M -b -v "$(cat wscript | awk 'sub("^VERSION = ","")' | tr -d "'")~$(date +"%Y%m%d")git${{ github.event.pull_request.number || steps.slug.outputs.sha8 }}" -D focal "automated build"
         debuild -rfakeroot --no-lintian || true
     - uses: actions/upload-artifact@v2