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>

classes/cargo.bbclass

@@ -9,11 +9,11 @@ inherit cargo_common
 CARGO = "cargo"
 
 # We need cargo to compile for the target
-BASEDEPENDS:append = " cargo-native"
+BASEDEPENDS_append = " cargo-native"
 
 # Ensure we get the right rust variant
-DEPENDS:append:class-target = " virtual/${TARGET_PREFIX}rust ${RUSTLIB_DEP}"
-DEPENDS:append:class-native = " rust-native"
+DEPENDS_append_class-target = " virtual/${TARGET_PREFIX}rust ${RUSTLIB_DEP}"
+DEPENDS_append_class-native = " rust-native"
 
 # Enable build separation
 B = "${WORKDIR}/build"