manifest: Re-add top-level Android.bp symlink

* The build system really, really, wants this one to stick around

Change-Id: Ie1956138d8c19d321a1806f44d9a3bad8b23fdae

default.xml

@@ -32,6 +32,7 @@
   <project path="build/blueprint" name="platform/build/blueprint" groups="pdk,tradefed" remote="aosp" />
   <project path="build/kati" name="LineageOS/android_build_kati" groups="pdk,tradefed" />
   <project path="build/soong" name="LineageOS/android_build_soong" groups="pdk,tradefed" >
+    <linkfile src="root.bp" dest="Android.bp" />
     <linkfile src="bootstrap.bash" dest="bootstrap.bash" />
   </project>
   <project path="art" name="LineageOS/android_art" groups="pdk" />