community/afl++: add run-time dependency on compiler-rt

Compiler-rt ships the files necessary to use afl++ with ASAN (Address Sanitizer) instrumentation. ASAN instrumentation can be enabled for afl-cc using AFL_USE_ASAN=1. While, strictly speaking, ASAN instrumentation is optional I would argue that it will be used in 99% of fuzzing cases anyhow (since without error detection instrumentation one will miss many bugs) and hence I believe that compiler-rt should be a dependency of afl++.