Added rust support

Rust relies on atomic builtins, which are not implemented in libgcc for
ARM. One is implemented in rust, which is sufficient to get the
current rust test to run.

Issue #1899

repos/base/run/rust.run

@@ -0,0 +1,27 @@
+build "core init test/rust"
+
+create_boot_directory
+
+install_config {
+	<config>
+		<parent-provides>
+			<service name="LOG"/>
+			<service name="RM"/>
+                        <service name="ROM"/>
+		</parent-provides>
+		<default-route>
+			<any-service> <parent/> </any-service>
+		</default-route>
+		<start name="rust-test">
+			<resource name="RAM" quantum="10M"/>
+		</start>
+	</config>
+}
+
+build_boot_image "core init rust-test ld.lib.so libc.lib.so"
+
+append qemu_args "-nographic -m 64"
+
+run_genode_until { 42 } 10
+
+puts "Test succeeded"