We only had the single `clang` symlink, but in case its useful to use
the toolchain with some other build system that expects `clang++`, or
even `clang-cl` or `clang-cpp`, fill in the rest of the symlinks.
The different `clang` flavors don't really need anything to support in
the subcommand as there is already an excellent way to get the exact
behavior of these names using Clang's `--driver-mode` flag, so these
just use that. That makes this change really *only* about busybox
behavior.
We don't really have a dedicated test path for things that are only
exposed via the symlinks, so I've added a simple Python integration test
we can use for that. I can backfill some testing of other symlinks if
useful (the `ld.lld` one might be worthwhile), although there is minimal
interesting logic to cover there.
Adds scripts/calculate_release_shas.py to print the versions, and
updates tool versions. Consolidates target-determinator logic with the
other tool logic.
This is also intended to make it easier to add more tools.
Chandler Carruth
Jon Ross-Perkins
