libstd-rs: use cargo_util_do_compile

classes/cargo_util.bbclass

@@ -88,8 +88,6 @@ EOF
 }
 
 cargo_util_do_compile () {
-	cd "${B}"
-
 	# prevent cargo from trying to fetch down new data
 	mkdir -p "${WORKDIR}/cargo_home/registry/index/github.com-1ecc6299db9ec823"
 	touch "${WORKDIR}/cargo_home/registry/index/github.com-1ecc6299db9ec823/.cargo-index-lock"

recipes-devtools/rust/libstd-rs.bb

@@ -23,12 +23,10 @@ RUSTFLAGS += "-L ${STAGING_LIBDIR}"
 
 B = "${WORKDIR}/build"
 
-do_compile () {
+do_compile_prepend () {
     cd ${S}/src/rustc/std_shim
     export CARGO_TARGET_DIR="${B}"
     export RUSTC_BOOTSTRAP_KEY="e8edd0fd"
-    oe_cargo_fix_env
-    oe_cargo_build
 }
 
 do_install () {