chore(release): 1.0.0-alpha.12 [skip ci]

# [1.0.0-alpha.12](https://git.gitlab.arm.com/bazel/rules_toolchain/compare/v1.0.0-alpha.11...v1.0.0-alpha.12) (2023-12-13)

### Bug Fixes

* better `uname` processing ([65ff62a2](https://git.gitlab.arm.com/bazel/rules_toolchain/commit/65ff62a27f8d3fdbc2d8165402031248dbbdfaf1))

### Features

* add MacOS triplet detection ([fbc8e8ea](https://git.gitlab.arm.com/bazel/rules_toolchain/commit/fbc8e8ea6dc7c422cd33bbb4106c923cab3e7bd0))