cerbero: Fix rustc detection in Meson when cross-compiling
This was causing issues when building gstreamer!3889 (merged) with -c config/cross-macos-universal.cbc
- example failing pipeline here.
Basically Meson couldn't find the Rust compiler for the non-native target. To fix that, we need to make Meson pass the Rust target triple (aarch64-apple-darwin/x86_64-apple-darwin
in this case) to rustc
. This was achieved by saving those args to the Meson cross file.