Build scripts that compile C/C++ (cc crate, libduckdb-sys's bundled
DuckDB, ring's assembly) are not cached by RUSTC_WRAPPER and dominate
warm CI time on Rust projects with heavy native deps. Export
CC=sccache cc and CXX=sccache c++ so those compilations land in the
same sccache backend as rustc.
Gated behind a new sccache-wrap-cc input (default "true") so callers
with build systems that do not tolerate multi-word CC/CXX can opt out.
Co-authored-by: Cursor <cursoragent@cursor.com>
