Ship the Rust standard library's COPYRIGHT file in release archives

The Rust standard library (std, core, alloc, compiler_builtins,
hashbrown, libc, etc.) is statically linked into every compiled Rust
binary. It is dual-licensed under Apache-2.0 OR MIT, and — unlike
GCC's runtime library — has no linking exception that would exempt
binary distributions from attribution requirements.

This is a known gap in the Rust ecosystem:

  * "Does the standard library have linking exceptions to their
    licensing?" — the answer is no.
    https://internals.rust-lang.org/t/does-the-standard-library-have-linking-exceptions-to-their-licensing/11377

  * "It's unclear exactly what license text must be included in a
    Rust binary" — open since 2019, still unresolved.
    rust-lang/rust#67014

The Rust toolchain ships a COPYRIGHT-library.html file at
$(rustc --print sysroot)/share/doc/rust/COPYRIGHT-library.html that
lists every component of the standard library, its license, its
copyright holders, and (for out-of-tree deps) the full license text.
Copy this file into each release archive as RUST-STDLIB-COPYRIGHT.html
so that anyone distributing gix/ein binaries has the attribution
material the license requires.

If a future toolchain version moves or removes the file, the step
warns but does not fail the build — the file is authoritative when
present but we should not break releases over a toolchain layout
change.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: EliahKagan

.github/workflows/release.yml

@@ -303,6 +303,20 @@ jobs:
           cp -- "${out_dirs[0]}/third_party_licenses.txt"  "$ARCHIVE/THIRD-PARTY-LICENSES.txt"
           cp -- "${out_dirs[0]}/third_party_licenses.json" "$ARCHIVE/THIRD-PARTY-LICENSES.json"
 
+          # The Rust standard library is statically linked into every
+          # Rust binary and is dual-licensed under Apache-2.0 OR MIT
+          # with NO linking exception (unlike GCC's runtime). Ship its
+          # own COPYRIGHT file so users have the attribution material
+          # the license requires. The file lives in the sysroot of
+          # whatever toolchain built this binary.
+          stdlib_copyright="$(rustc --print sysroot)/share/doc/rust/COPYRIGHT-library.html"
+          if [ -f "$stdlib_copyright" ]; then
+            cp -- "$stdlib_copyright" "$ARCHIVE/RUST-STDLIB-COPYRIGHT.html"
+          else
+            printf 'warning: %s not found — stdlib attribution will be missing from the archive\n' \
+              "$stdlib_copyright" >&2
+          fi
+
           # Validate the manifest: reject stubs, verify the JSON is
           # parseable and has the expected feature profile and a plausible
           # crate count, and confirm no crate is missing license text.