Make bitcoinfuzz "agnostic" and add support for AFL++

[brunoerg]

I strongly believe that we could find more bugs if we support other fuzzers than libfuzzer. We could follow the same approach of Bitcoin Core and make bitcoinfuzz "agnostic". It means that we could fuzz it using different fuzzers (libfuzzer, AFL, etc).

[brunoerg]

I think this a good start point for you @i-am-yuvi

[yuvicc]

Yes

[dergoegge]

Have you tried just using e.g. afl-clang-fast++ instead of clang? It also supports the fuzzer sanitizer flag and will link against it's own LLVMFuzzerTestOneInput driver, so you wouldn't really need to change anything about your build system.

[brunoerg]

Have you tried just using e.g. afl-clang-fast++ instead of clang? It also supports the fuzzer sanitizer flag and will link against it's own LLVMFuzzerTestOneInput driver, so you wouldn't really need to change anything about your build system.

I just tried it and worked fine, nice suggestion! I think it worth to add it on the documentation.