/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_incremental-329138e71f50a1d9.so is in libstd-rust-dev 1.24.1+dfsg1+llvm-0ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/../../../x86_64-linux-gnu/librustc_incremental-329138e71f50a1d9.so