Fix Windows GNU staticlib output naming

[cerisier]

Summary

Make Rust static-library naming ABI-aware on Windows.

Rust emits lib<crate>.a for the GNU and GNULLVM Windows ABIs, while MSVC emits <crate>.lib. The generated Rust toolchain currently selects .lib from the operating system alone, and determine_lib_name removes the lib prefix for every Windows static library. As a result, Bazel declares an output different from the file emitted by rustc for Windows GNU-like targets.

This change passes the target ABI through repository and toolchain generation, selects .a for Windows GNU/GNULLVM static libraries, and preserves their lib prefix. MSVC behavior and Windows dynamic-library naming remain unchanged.

Regression coverage exercises the extension mapping, rendered toolchain metadata, final GNU/GNULLVM/MSVC static-library names, and the unchanged GNU cdylib name.

[UebelAndre]

Thank you!