cargo_util: simplified cargo bbclass for crates

The existing cargo class attempts to jump through a few hoops for
settings that are not necessarily with newer versions of cargo.

classes/cargo_util.bbclass

@@ -0,0 +1,87 @@
+# add crate fetch support
+inherit crate-fetch
+
+# the binary we will use
+CARGO = "cargo"
+
+# Where we download our registry and dependencies to
+export CARGO_HOME = "${WORKDIR}/cargo_home"
+
+# We need cargo to compile for the target
+BASEDEPENDS_append = " cargo-native"
+
+# Ensure we get the right rust variant
+DEPENDS_append_class-target = "virtual/${TARGET_PREFIX}rust"
+
+# Cargo only supports in-tree builds at the moment
+B = "${S}"
+
+# In case something fails in the build process, give a bit more feedback on
+# where the issue occured
+export RUST_BACKTRACE = "1"
+
+# The pkg-config-rs library used by cargo build scripts disables itself when
+# cross compiling unless this is defined. We set up pkg-config appropriately
+# for cross compilation, so tell it we know better than it.
+export PKG_CONFIG_ALLOW_CROSS = "1"
+
+# All the rust & cargo ecosystem assume that CC, LD, etc are a path to a single
+# command. Fixup the ones we give it so that is the case.
+# XXX: this is hard coded based on meta/conf/bitbake.conf
+# TODO: we do quite a bit very similar to this in rust.inc, see if it can be
+# generalized.
+export RUST_CC = "${CCACHE}${HOST_PREFIX}gcc"
+export RUST_CFLAGS = "${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS} ${CFLAGS}"
+export RUST_BUILD_CC = "${CCACHE}${BUILD_PREFIX}gcc"
+export RUST_BUILD_CFLAGS = "${BUILD_CC_ARCH} ${BUILD_CFLAGS}"
+
+export CARGO_BUILD_FLAGS = "-v --target ${HOST_SYS} --release"
+
+# This is based on the content of CARGO_BUILD_FLAGS and generally will need to
+# change if CARGO_BUILD_FLAGS changes.
+export CARGO_TARGET_SUBDIR="${HOST_SYS}/release"
+oe_cargo_build () {
+	bbnote "cargo = $(which cargo)"
+	bbnote "rustc = $(which rustc)"
+	bbnote "${CARGO} build ${CARGO_BUILD_FLAGS} $@"
+	"${CARGO}" build ${CARGO_BUILD_FLAGS} "$@"
+}
+
+oe_cargo_fix_env () {
+	export CC="${RUST_CC}"
+	export CFLAGS="${RUST_CFLAGS}"
+	export AR="${AR}"
+	export TARGET_CC="${RUST_CC}"
+	export TARGET_CFLAGS="${RUST_CFLAGS}"
+	export TARGET_AR="${AR}"
+	export HOST_CC="${RUST_BUILD_CC}"
+	export HOST_CFLAGS="${RUST_BUILD_CFLAGS}"
+	export HOST_AR="${BUILD_AR}"
+}
+
+cargo_util_do_compile () {
+	cd "${B}"
+
+    # prevent cargo from trying to fetch down new data
+    touch "${WORKDIR}/cargo_home/registry/index/.cargo-index-lock"
+
+	oe_cargo_fix_env
+	oe_cargo_build
+}
+
+# All but the most simple projects will need to override this.
+cargo_util_do_install () {
+	local have_installed=false
+	install -d "${D}${bindir}"
+	for tgt in "${B}/target/${CARGO_TARGET_SUBDIR}/"*; do
+		if [ -f "$tgt" ] && [ -x "$tgt" ]; then
+			install -m755 "$tgt" "${D}${bindir}"
+			have_installed=true
+		fi
+	done
+	if ! $have_installed; then
+		die "Did not find anything to install"
+	fi
+}
+
+EXPORT_FUNCTIONS do_compile do_install