Add support for clang about american-fuzzy-lop HOT 2 CLOSED

Are you able to build and fuzz instrumented binaries with clang?

Marking as dupe for now; I do not believe that the instrumentation will work 
with clang, so removing the check would defeat the purpose. 

(If the instrumentation somehow does work, please reopen and provide additional 
information.)

Afl may be eventually adopted to use clang edge coverage support or to 
otherwise work with the code they emit, but that's aready on the TODO list in 
docs/.