rust: use a shared source location for all the packages needing the rustc source tree

classes/shared-source-provide.bbclass

@@ -0,0 +1,38 @@
+# In order to share the same source between multiple packages (.bb files), we
+# unpack and patch the X source here into a shared dir.
+#
+# Take a look at gcc-source.inc for the general structure of this
+
+# We require that "SOURCE_NAME" be set
+
+# nopackages.bbclass {
+deltask do_package
+deltask do_package_write_rpm
+deltask do_package_write_ipk
+deltask do_package_write_deb
+deltask do_package_qa
+deltask do_packagedata
+#}
+
+deltask do_configure
+deltask do_compile
+deltask do_install
+deltask do_populate_sysroot
+deltask do_populate_lic
+deltask do_rm_work
+
+
+# override to get rid of '-native' or other misc
+# XXX: consider ${PR}
+PN = "${SOURCE_NAME}-source-${PV}"
+WORKDIR = "${TMPDIR}/work-shared/${SOURCE_NAME}-${PV}-${PR}"
+SSTATE_SWSPEC = "sstate:${SOURCE_NAME}::${PV}:${PR}::${SSTATE_VERSION}:"
+
+STAMP = "${STAMPS_DIR}/work-shared/${SOURCE_NAME}-${PV}-${PR}"
+STAMPCLEAN = "${STAMPS_DIR}/work-shared/${SOURCE_NAME}-${PV}-*"
+
+INHIBIT_DEFAULT_DEPS = "1"
+DEPENDS = ""
+PACKAGES = ""
+
+EXCLUDE_FROM_WORLD = "1"

classes/shared-source-use.bbclass

@@ -0,0 +1,4 @@
+S = "${TMPDIR}/work-shared/${SOURCE_NAME}-${PV}-${PR}"
+
+do_configure[depends] += "${SOURCE_NAME}-source-${PV}:do_patch"
+do_populate_lic[depends] += "${SOURCE_NAME}-source-${PV}:do_unpack"