Reserve 'init'.

This makes `pathmod init` and `gomod init` work, and it also reserves
the 'init' for potential future usage.

Change-Id: I6990bf421211b93d58d978d84d46474ff243e808
Bugs: me
Test: pathmod init; gomod init

init/Android.bp

@@ -159,6 +159,13 @@ cc_library_static {
     },
 }
 
+phony {
+    name: "init",
+    required: [
+        "init_second_stage",
+    ],
+}
+
 cc_binary {
     name: "init_second_stage",
     recovery_available: true,