Completely migrate init first stage to Soong

adb_debug.prop is migrated too. And ramdisk_available is added to all
dependencies.

Bug: 187196593
Test: boot
Change-Id: I59cd149e0021211b8fd59c44b93bbf18dc8637bf
diff --git a/rootdir/Android.bp b/rootdir/Android.bp
index ae21633..e98733a 100644
--- a/rootdir/Android.bp
+++ b/rootdir/Android.bp
@@ -45,4 +45,11 @@
     src: "etc/public.libraries.android.txt",
     filename: "public.libraries.txt",
     installable: false,
-}
\ No newline at end of file
+}
+
+// adb_debug.prop in debug ramdisk
+prebuilt_root {
+    name: "adb_debug.prop",
+    src: "adb_debug.prop",
+    debug_ramdisk: true,
+}