Deprecate USER in favor of BUILD_USERNAME
Bug: 122270019
Test: treehugger, codesearch
diff --git a/Changes.md b/Changes.md
index 2d5cd97..1ed6bf8 100644
--- a/Changes.md
+++ b/Changes.md
@@ -1,5 +1,15 @@
# Build System Changes for Android.mk Writers
+## `USER` deprecation {#USER}
+
+`USER` will soon be `nobody` in many cases due to the addition of a sandbox
+around the Android build. Most of the time you shouldn't need to know the
+identity of the user running the build, but if you do, it's available in the
+make variable `BUILD_USERNAME` for now.
+
+Similarly, the `hostname` tool will also be returning a more consistent value
+of `android-build`. The real value is available as `BUILD_HOSTNAME`.
+
## `BUILD_NUMBER` removal from Android.mk {#BUILD_NUMBER}
`BUILD_NUMBER` should not be used directly in Android.mk files, as it would