Add Rust toolchain

Needed to set CONFIG_RUST_IS_AVAILABLE.

Bug: 270672379
Test: repo sync. prebuilts/rust appears
Change-Id: Ica9895755452e5b37f6f35d9e63c8984e79a338b
1 file changed
tree: e1f99ab8cb66e4f592c8b395b3d20c2ba158a103
  1. default.xml