[libFuzzer] Add a missing include_directories.

Summary: FuzzerInterceptors.cpp includes <sanitizer/common_interface_defs.h>, and this patch adds a missing include_directories to make sure the included file is found.

Reviewers: morehouse, hctim, dmajor

Subscribers: mgorny, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D84474