Move libLLVM prebuilt to Android.bp

Test: m -j checkbuild
Change-Id: Ibd1a36d6b005e7d6938a8467787906012a3fdc39
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..a47266b
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1 @@
+subdirs=["tools"]