Update clang-sys dependency
Update clang-sys dependency

Version 1.0.2 of clang-sys fixes an issue that was causing upstream
builds on macOS 11.0 to fail when it couldn't find LLVM configs
properly.

https://github.com/KyleMayes/clang-sys/blob/master/CHANGELOG.md#102---2020-11-17
https://github.com/KyleMayes/clang-sys/pull/118

rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen