Revert "Convert to new override syntax (#357)"

This commit is not compatible with zeus layer so revert it.

This reverts commit bf6705fb7f.

Signed-off-by: Clément Péron <peron.clem@gmail.com>

recipes-devtools/cargo/cargo.inc

@@ -25,7 +25,7 @@ do_cargo_setup_snapshot () {
 addtask cargo_setup_snapshot after do_unpack before do_configure
 do_cargo_setup_snapshot[dirs] += "${WORKDIR}/${CARGO_SNAPSHOT}"
 
-do_compile:prepend () {
+do_compile_prepend () {
 	export RUSTC_BOOTSTRAP="1"
 }
 
@@ -47,5 +47,5 @@ BBCLASSEXTEND = "native nativesdk"
 
 # When building cargo-native we don't have cargo-native to use and depend on,
 # so we must use the locally set up snapshot to bootstrap the build.
-BASEDEPENDS:remove:class-native = "cargo-native"
-CARGO:class-native = "${WORKDIR}/${CARGO_SNAPSHOT}/bin/cargo"
+BASEDEPENDS_remove_class-native = "cargo-native"
+CARGO_class-native = "${WORKDIR}/${CARGO_SNAPSHOT}/bin/cargo"