Add busybox to Mendel manifest

Change-Id: I8cf526ee5d4680aaeb545bab277c42ce1febf2ef
diff --git a/mendel.xml b/mendel.xml
index d6745bc..22c9ac4 100644
--- a/mendel.xml
+++ b/mendel.xml
@@ -20,6 +20,7 @@
     <project path="tools/bpt" name="bpt" />
     <project path="tools/img2simg" name="img2simg" />
     <project path="tools/mdt" name="mdt" />
+    <project path="tools/busybox" name="busybox" />
     <!-- END Misc Tools repos -->
 
     <!-- BEGIN Package repos -->