first_stage_init: add hook to exec a shell script

If the first stage console is being used, attempt to run /first_stage.sh
immediately before the console is created.

Bug: 154126020
Change-Id: I8b7431e7b8219afea295b120d7ea91751804bda6
diff --git a/init/Android.mk b/init/Android.mk
index b49fb3b..416b732 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -50,6 +50,7 @@
 LOCAL_SRC_FILES := \
     block_dev_initializer.cpp \
     devices.cpp \
+    first_stage_console.cpp \
     first_stage_init.cpp \
     first_stage_main.cpp \
     first_stage_mount.cpp \