Preserve metadata and prevent redundant disk writes during builds with
the install's -C (compare) flag.
The previous historical comparison limit of 16MB is insufficient for
modern toolchains, frequently choked or bypassed by a large base
components like LLVM/Clang, kernels, Rust apps, and large runtime
libraries.
By leaving matching files alone, install keeps their modification timestamps
intact. make(1) safely ignores those files on subsequent runs.
Base examples: 15.0 amd64 GENERIC kernel - 28MB, clang - 105MB, lldb - 97MB, etc.