Switch to rustbuild

Switch the build process to using Rust's new build system called
rustbuild. At the same time stop using jemalloc on all platforms and
switch to the system allocator since that was simplier to do.

recipes-devtools/rust/libstd-rs.inc

@@ -2,7 +2,7 @@ SUMMARY = "Rust standard libaries"
 HOMEPAGE = "http://www.rust-lang.org"
 SECTION = "devel"
 LICENSE = "MIT | Apache-2.0"
-LIC_FILES_CHKSUM ="file://COPYRIGHT;md5=43e1f1fb9c0ee3af66693d8c4fecafa8"
+LIC_FILES_CHKSUM ="file://../../COPYRIGHT;md5=43e1f1fb9c0ee3af66693d8c4fecafa8"
 
 RUSTLIB_DEP = ""
 inherit cargo
@@ -10,16 +10,16 @@ inherit cargo
 # Needed so cargo can find libbacktrace
 RUSTFLAGS += "-L ${STAGING_LIBDIR}"
 
+S = "${RUSTSRC}/src/libstd"
+
 do_compile_prepend () {
-    cd ${S}/src/rustc/std_shim
     export CARGO_TARGET_DIR="${B}"
-    # For Rust 1.12.1 and lower
-    export RUSTC_BOOTSTRAP_KEY="${RS_KEY}"
     # For Rust 1.13.0 and newer
     export RUSTC_BOOTSTRAP="1"
 }
 
 do_install () {
     mkdir -p ${D}${rustlibdir}
+
     cp ${B}/${TARGET_SYS}/release/deps/* ${D}${rustlibdir}
 }