[libfuzzer] Roll libfuzzer to 64bdf915852b7a8c2b81013682d77e003280168b

Changes:

https://chromium.googlesource.com/chromium/llvm-project/llvm/lib/Fuzzer/+log/4d737af21c2ce9e8b0655cd9397d83fa7956406c..64bdf915852b7a8c2b81013682d77e003280168b

BUG=

Review-Url: https://codereview.chromium.org/2669243011
Cr-Commit-Position: refs/heads/master@{#448077}
2 files changed