Separate init packaging for mainline

With system-as-root, both first and second stage init belong to
system, but without system-as-root, first stage belongs to vendor and
second stage belongs to system.  This change references two phony
packages that include the right parts of init for systen and vendor.

Bug: 117606184
Test: mainline builds work properly
Change-Id: I997309655fef28cb1c3d4b3be989c035b5c6488d
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 11f5fe4..57e981f 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -85,9 +85,9 @@
     incidentd \
     incident_helper \
     incident_report \
-    init \
     init.environ.rc \
     init.rc \
+    init_system \
     input \
     installd \
     iorapd \