Mitigation:

In your base afl directory (i.e. in afl-2.52b), run following:
make && make -C llvm_mode LLVM_CONFIG=llvm-config-6.0 CC=clang-6.0


Full installation steps:

cd ~/AFL && wget http://lcamtuf.coredump.cx/afl/releases/afl-latest.tgz
tar xzf afl-latest-X.tgz
make && make -C llvm_mode LLVM_CONFIG=llvm-config-6.0 CC=clang-6.0
