This only works on Linux!
bazel --config=asan-libfuzzer //experimental/protobuf:lldb_eval_fuzzer_run # or bazel --config=asan-libfuzzer //experimental/fuzzed_rng:lldb_eval_fuzzer_run
Use --config=libfuzzer instead of --config=asan-libfuzzer to disable address sanitizer.
If you're changing structure of proto messages, you might encounter ERRORs when running fuzzer. Try to clear /tmp/fuzzing folder where corpus and artifacts of previous runs were saved.