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.

(cherry picked from commit a4fe235317)

recipes-devtools/cargo/cargo-0.16.0.inc

@@ -1,5 +1,11 @@
-
 CARGO_SNAPSHOT = "2016-09-01/cargo-nightly-x86_64-unknown-linux-gnu.tar.gz;downloadfilename=cargo-nightly-x86_64-unknown-linux-gnu-2016-09-01.tar.gz"
 SRC_URI[cargo-snapshot.md5sum] = "d41ebf79290a7c9c9e5df87cb27e5091"
 SRC_URI[cargo-snapshot.sha256sum] = "365e5cad79512d244b8ced32f8e5b86a710fc6c17f0d0f5f744b8058ef6dc756"
 
+SRC_URI += "\
+	https://static.rust-lang.org/cargo-dist/${CARGO_SNAPSHOT};name=cargo-snapshot \
+"
+
+# When building cargo-native we don't have a built cargo to use so we must use
+# the snapshot to bootstrap the build of cargo
+CARGO_class-native = "${WORKDIR}/cargo-nightly-${RUST_BUILD_SYS}/cargo/bin/cargo"

recipes-devtools/cargo/cargo.inc

@@ -2,10 +2,6 @@ SECTION = "devel"
 
 DEPENDS = "openssl zlib libgit2 curl ca-certificates libssh2"
 
-SRC_URI += "\
-	https://static.rust-lang.org/cargo-dist/${CARGO_SNAPSHOT};name=cargo-snapshot \
-"
-
 LIC_FILES_CHKSUM += " \
 file://LICENSE-THIRD-PARTY;md5=892ea68b169e69cfe75097fc38a15b56 \
 "
@@ -13,8 +9,4 @@ file://LICENSE-THIRD-PARTY;md5=892ea68b169e69cfe75097fc38a15b56 \
 # Used in libgit2-sys's build.rs, needed for pkg-config to be used
 export LIBGIT2_SYS_USE_PKG_CONFIG = "1"
 
-# When building cargo-native we don't have a built cargo to use so we must use
-# the snapshot to bootstrap the build of cargo
-CARGO_class-native = "${WORKDIR}/cargo-nightly-${RUST_BUILD_SYS}/cargo/bin/cargo"
-
 BBCLASSEXTEND = "native"