nativesdk: Add some tools in a separate recipe (#345)

* nativesdk: Add some tools in a separate recipe

This brings ATM:
- clippy
- rustfmt

Another approach might be to include these into the existing rust recipe,
but as we can't really use PACKAGECONFIG here it might just overload it.
This way, the tools will be built in parallel and still can be excluded
from the packgae group, if desired.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

recipes-devtools/rust/rust.inc

@@ -117,11 +117,13 @@ python do_configure() {
 
     config.set("build", "vendor", e(True))
 
-    targets = [d.getVar("TARGET_SYS", True)]
+    if not "targets" in locals():
+        targets = [d.getVar("TARGET_SYS", True)]
     config.set("build", "target", e(targets))
 
-    hosts = [d.getVar("HOST_SYS", True)]
-    config.set("build", "host", e(targets))
+    if not "hosts" in locals():
+        hosts = [d.getVar("HOST_SYS", True)]
+    config.set("build", "host", e(hosts))
 
     # We can't use BUILD_SYS since that is something the rust snapshot knows
     # nothing about when trying to build some stage0 tools (like fabricate)