Copying debug ramdisk files to /debug_ramdisk/*

In previous implementation, userdebug sepoilcy and property files are
loaded from the system.img. This CL changes this to:

  - first-stage init copies userdebug files from ramdisk to /debug_ramisk/*
  - second-stage init loads files from /debug_ramdisk/*.

Note: same as before, the above can only be triggered, if the device
is UNLOCKED

With this, we don't have to put userdebug related files into the USER
system.img.

Bug: 126493225
Test: boot device with a ramdisk with /force_debuggable, checks related
      files are loaded
Change-Id: I63f5f846e82ba78427062bf7615c26173878d8f3
Merged-In: I63f5f846e82ba78427062bf7615c26173878d8f3
(cherry picked from commit 30afda71c0dac4d1d59a91b78256ebff76257ad8)
diff --git a/rootdir/Android.mk b/rootdir/Android.mk
index 5d307b8..a97858a 100644
--- a/rootdir/Android.mk
+++ b/rootdir/Android.mk
@@ -97,7 +97,7 @@
 #
 # create some directories (some are mount points) and symlinks
 LOCAL_POST_INSTALL_CMD := mkdir -p $(addprefix $(TARGET_ROOT_OUT)/, \
-    sbin dev proc sys system data odm oem acct config storage mnt apex $(BOARD_ROOT_EXTRA_FOLDERS)); \
+    sbin dev proc sys system data odm oem acct config storage mnt apex debug_ramdisk $(BOARD_ROOT_EXTRA_FOLDERS)); \
     ln -sf /system/bin $(TARGET_ROOT_OUT)/bin; \
     ln -sf /system/etc $(TARGET_ROOT_OUT)/etc; \
     ln -sf /data/user_de/0/com.android.shell/files/bugreports $(TARGET_ROOT_OUT)/bugreports; \