build: Override host metadata

* Matches the Android 12 build sandbox: https://android.googlesource.com/platform/build/+/refs/tags/android-12.0.0_r2/Changes.md

Change-Id: I032127e2724b34e649bcc73c347c8e67df1f45b0
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
diff --git a/build/envsetup.sh b/build/envsetup.sh
index ba19ba1..3ca2af3 100644
--- a/build/envsetup.sh
+++ b/build/envsetup.sh
@@ -1090,3 +1090,7 @@
     fi
     return $?
 }
+
+# Override host metadata to make builds more reproducible and avoid leaking info
+export BUILD_USERNAME=nobody
+export BUILD_HOSTNAME=android-build