add some readme notes

README.md

@@ -10,17 +10,23 @@ This openembedded layer provides the rust compiler, tools for building packages
 
 ## What doesn't:
 
- - building cargo-native (I managed to break it)
+ - building cargo-native (Using a local cargo install from somewhere else works just fine).
 
 ## What's untested:
 
  - cargo, rust (built for target)
  - running anything
+ - Other TARGETs
 
 ## TODO
 
- - Use rust-native when building rust & rust-cross
  - Include downloaded stage0 snapshot in `SRC_URI`
+ - -crosssdk and -buildsdk packages
+ - -runtime? (install target libraries on target)
+
+## Pitfalls
+
+ - TARGET_SYS _must_ be different from BUILD_SYS. This is due to the way configuration options are tracked for different targets.
 
 ## Dependencies