[libfuzzer] Fix build error due to out-of-line definition of 'Fuzzer' does not match...

[libfuzzer] Fix build error due to out-of-line definition of 'Fuzzer' does not match any declaration in 'fuzzer::Fuzzer' (NFC)

/data/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:138:9: error: out-of-line definition of 'Fuzzer' does not match any declaration in 'fuzzer::Fuzzer'
Fuzzer::Fuzzer(UserCallback CB, InputCorpus &Corpus, MutationDispatcher &MD,
        ^~~~~~
/data/llvm-project/compiler-rt/lib/fuzzer/FuzzerInternal.h:35:10: note: type of 4th parameter of member declaration does not match definition ('fuzzer::FuzzingOptions &' vs 'const fuzzer::FuzzingOptions &')
         FuzzingOptions &Options);
         ^
1 error generated.