cargo.eclass: Enable cross-compiling by setting environment variables

CARGO_BUILD_TARGET and CARGO_TARGET_<triple>_LINKER are enough for pure
Rust. The linker otherwise defaults to `cc`. This doesn't respect any
linker specified in LDFLAGS, but this is also true for native builds. We
would need to do something with RUSTFLAGS.

The HOST_* variables are for the cc-rs crate, which is often used to
build non-Rust code. It uses the usual variables (CC, CFLAGS, etc) for
the target.

Signed-off-by: James Le Cuirot <chewi@gentoo.org>

0 files changed, 0 insertions, 0 deletions