add rust 1.49.0

Now it seems `./x.py install` is the only way to assemble a fully
working stage 2 cross-built compiler. See rust-lang/rust#81702.

recipes-devtools/rust/rust_1.49.0.bb

@@ -0,0 +1,24 @@
+require rust.inc
+require rust-source-${PV}.inc
+require rust-snapshot-${PV}.inc
+
+SRC_URI += "\
+    file://0001-rustc_target-Fix-dash-vs-underscore-mismatches-in-op.patch \
+    "
+
+DEPENDS += "rust-llvm (=${PV})"
+
+# Otherwise we'll depend on what we provide
+INHIBIT_DEFAULT_RUST_DEPS_class-native = "1"
+# We don't need to depend on gcc-native because yocto assumes it exists
+PROVIDES_class-native = "virtual/${TARGET_PREFIX}rust"
+
+do_compile () {
+    rust_runx build --stage 2
+}
+
+rust_do_install() {
+    rust_runx install
+}
+
+BBCLASSEXTEND = "native"