msan doesn't understand sscanf with %ms, so it falsely reports unitialized
memory. Using sscanf with %ms is quite convenient in
socket_address_parse_netlink(), so let's just not run the fuzzer for
ListenNetlink= at all for now. If msan is fixed, we can remove this.
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=6884
fuzz-unit-file generated too much logs about invalid config lines. This just
slows things down and fills the logs. If necessary, it's better to rerun the
interesting cases with SYSTEMD_LOG_LEVEL=debug.
The fuzzers will be used by oss-fuzz to automatically and
continuously fuzz systemd.
This commit includes the build tooling necessary to build fuzz
targets, and a fuzzer for the DNS packet parser.
