security/afl++: Update to 3.14c

Build two flavors, one compiled with LLVM13 and one with GCC. Mixing
compilers in the same build is too complicated for casual maintainance.
The flavors are installed into their own prefixes in /usr/local/afl++-gcc
and /usr/local/afl++-llvm which also solves the conflict with
security/afl.

Changes: https://github.com/AFLplusplus/AFLplusplus/blob/3.14c/docs/Changelog.md#version-314c-release