Mount binderfs

Mount binderfs at /dev/binderfs. Also add symlinks from /dev/binder,
/dev/hwbinder and /dev/vndbinder to /dev/binderfs/binder,
/dev/binderfs/hwbinder and /dev/binderfs/vndbinder respectively.

Bug: 136497735
Test: Cuttlefish boots on Android Common Kernel 4.19 with kernel config
CONFIG_ANDROID_BINDERFS=y.

Change-Id: I349face22a2e73bfd79af0188e41188c323388f7
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 7f4f025..30f273e 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -69,6 +69,19 @@
     mkdir /dev/boringssl 0755 root root
     mkdir /dev/boringssl/selftest 0755 root root
 
+    # Mount binderfs
+    mkdir /dev/binderfs
+    mount binder binder /dev/binderfs stats=global
+    chmod 0755 /dev/binderfs
+
+    symlink /dev/binderfs/binder /dev/binder
+    symlink /dev/binderfs/hwbinder /dev/hwbinder
+    symlink /dev/binderfs/vndbinder /dev/vndbinder
+
+    chmod 0666 /dev/binderfs/hwbinder
+    chmod 0666 /dev/binderfs/binder
+    chmod 0666 /dev/binderfs/vndbinder
+
 # Run boringssl self test for each ABI so that later processes can skip it. http://b/139348610
 on early-init && property:ro.product.cpu.abilist32=*
     exec_start boringssl_self_test32