tests: make fuzzbuzz.sh compatible with Azure Pipelines again

Now that https://github.com/systemd/systemd/pull/12542 is merged,
fuzzbuzz.sh should be changed a little bit to make it work
on Azure Pipelines. We can no longer assume that source repositories
are added "automagically" by Travis CI or that PATH is set properly.

travis-ci/managers/fuzzbuzz.sh

@@ -6,12 +6,14 @@ set -u
 
 REPO_ROOT=${REPO_ROOT:-$(pwd)}
 
+sudo bash -c "echo 'deb-src http://archive.ubuntu.com/ubuntu/ xenial main restricted universe multiverse' >>/etc/apt/sources.list"
 sudo apt-get update -y
 sudo apt-get build-dep systemd -y
 sudo apt-get install -y ninja-build python3-pip python3-setuptools
 pip3 install meson
 
 cd $REPO_ROOT
+export PATH="$HOME/.local/bin/:$PATH"
 tools/oss-fuzz.sh
 timeout --preserve-status 5 ./out/fuzz-unit-file
 git clean -dxff