Add a changes file for bug22830.

changes/bug22830

@@ -0,0 +1,5 @@
+ o Minor bugfixes:
+   - Fix a problem with Rust toolchains not being found when building
+     without --enable-cargo-online-mode, due to setting the $HOME
+     environment variable instead of $CARGO_HOME.  Fixes bug 22830;
+     fix by Chelsea Komlo.  Bugfix on 0.3.1.1-alpha.