Document the preferred branch for each device

Change-Id: I5bca7dc507f33bbc970246a8a155d73abdab8a65
diff --git a/src/source/building-devices.md b/src/source/building-devices.md
index fd7bed7..6fda907 100644
--- a/src/source/building-devices.md
+++ b/src/source/building-devices.md
@@ -115,13 +115,13 @@
 The recommended builds for the various devices are available through
 the lunch menu, accesed when running the `lunch` command with no arguments:
 
-Device   | Build configuration
----------|---------------------
-crespo   | full_crespo-userdebug
-crespo4g | full_crespo4g-userdebug
-passion  | full_passion-userdebug
-sapphire | full_sapphire-userdebug
-dream    | full_dream-userdebug
+Device   | Branch           | Build configuration
+---------|------------------|------------------------
+crespo   | android-2.3.4_r1 | full_crespo-userdebug
+crespo4g | gingerbread      | full_crespo4g-userdebug
+passion  | android-2.3.4_r1 | full_passion-userdebug
+sapphire | android-2.2.2_r1 | full_sapphire-userdebug
+dream    | android-2.2.2_r1 | full_dream-userdebug
 
 ## Flashing a device ##