Compatibility with LLVM6.0 on soon-to-be-release nightly #29
Description
Rustc will very soon merge it's shinny new LLVM6.0 backend rust-lang/rust#47828.
It will break fuzzing with current libfuzzer because the generated coverage intrumentation will expect new symbols to be implemented by the linked fuzzer implementation.
The current libfuzzer in libfuzzer-sys is 4.0 and is missing those new symbols.
Upgrading libfuzzer source code to 6.0 while disabling sanitizers works well and is compatible with compiler using LLVM4.0 (so the transition will be easy).
However, begin able to compile with sanitizer enabled will need more work: for instance, to make sanitizer=address work, we will probably need to first package asan