libstd-rs: cross compile rust's runtime

This can replace rustlib, which just copies the binaries already
built by rust-cross.

recipes-devtools/rust/libstd-rs.bb

@@ -0,0 +1,30 @@
+SUMMARY = "Rust standard libaries"
+HOMEPAGE = "http://www.rust-lang.org"
+SECTION = "devel"
+LICENSE = "MIT | Apache-2.0"
+
+LIC_FILES_CHKSUM ="file://COPYRIGHT;md5=43e1f1fb9c0ee3af66693d8c4fecafa8"
+require rust-shared-source.inc
+
+DEPENDS += "compiler-rt"
+
+RUSTLIB_DEP = ""
+inherit cargo_util
+
+# Needed so cargo can find libbacktrace
+RUSTFLAGS += "-L ${STAGING_LIBDIR}"
+
+B = "${WORKDIR}/build"
+
+do_compile () {
+    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 () {
+    mkdir -p ${D}${rustlibdir}
+    cp ${B}/${TARGET_SYS}/release/deps/* ${D}${rustlibdir}
+}