This is a more ambitious version of https://github.com/rust-lang/rust/pull/98716.
It still changes the shebang back to python3, for compatibility with non-Unix systems,
but also adds alternative entrypoints for systems without `python3` installed.
These scripts will be necessary for the rust entrypoint (#94829), so I see
little downside in adding them early.
This commit is a rewrite of the user-facing interface to the rustbuild build
system. The intention here is to make it much easier to compile/test the project
without having to remember weird rule names and such. An overall view of the new
interface is:
# build everything
./x.py build
# document everyting
./x.py doc
# test everything
./x.py test
# test libstd
./x.py test src/libstd
# build libcore stage0
./x.py build src/libcore --stage 0
# run stage1 run-pass tests
./x.py test src/test/run-pass --stage 1
The `src/bootstrap/bootstrap.py` script is now aliased as a top-level `x.py`
script. This `x` was chosen to be both short and easily tab-completable (no
collisions in that namespace!). The build system now accepts a "subcommand" of
what to do next, the main ones being build/doc/test.
Each subcommand then receives an optional list of arguments. These arguments are
paths in the source repo of what to work with. That is, if you want to test a
directory, you just pass that directory as an argument.
The purpose of this rewrite is to do away with all of the arcane renames like
"rpass" is the "run-pass" suite, "cfail" is the "compile-fail" suite, etc. By
simply working with directories and files it's much more intuitive of how to run
a test (just pass it as an argument).
The rustbuild step/dependency management was also rewritten along the way to
make this easy to work with and define, but that's largely just a refactoring of
what was there before.
The *intention* is that this support is extended for arbitrary files (e.g.
`src/test/run-pass/my-test-case.rs`), but that isn't quite implemented just yet.
Instead directories work for now but we can follow up with stricter path
filtering logic to plumb through all the arguments.
