package/rust: build and install cargo

package/rust: build and install cargo

Cargo source code is not provided anymore as a separate tarball but is
now built along with the Rust compiler. So update rust host variant to
build Cargo.

For now, all this will be overwritten again by the host-cargo package,
but this package will be removed in later commits.

Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
Signed-off-by: Patrick Havelange <patrick.havelange@essensium.com>
Tested-by: Sam Voss <sam.voss@rockwellcollins.com>
[Arnout: merge all install commands in HOST_RUST_INSTALL_CMDS]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Tested-by: David Pierret <david.pierret@smile.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>