rust: build the default set of tools

rust: build the default set of tools

Setting it explicitly replaces rust's default choice which is rustdoc
(needed for example in selftests and otherwise expected to be present
in typical rust installations):

https://github.com/rust-lang/rust/blob/master/config.example.toml#L320

This addresses some of the rust selftest failures but not all. Help
is appreciate to restore the selftest.

Unfortunately, this also breaks rust reproducibility (or rather exposes
that it was never properly fixed, as explained here:
https://lists.openembedded.org/g/openembedded-core/message/199288
)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>