[libFuzzer] Break dependency on common_interface_defs.h

Some libFuzzer users build using the build.sh script, without access to
the <sanitizer/common_interface_defs.h> include.

Update https://github.com/rust-fuzz/libfuzzer/issues/65.

Reviewed By: dokyungs

Differential Revision: https://reviews.llvm.org/D86981