Add post fork hook for System Server

Adds a post fork hook for System Server that is used to enable JIT.

Bug: 62356545
Bug: 66095511
Test: device boots, no permission errors
Change-Id: I963e8c4903fb20fd0b5a207fdc6746035b69c569
diff --git a/core/java/com/android/internal/os/Zygote.java b/core/java/com/android/internal/os/Zygote.java
index 4ee950a..8b3829b3 100644
--- a/core/java/com/android/internal/os/Zygote.java
+++ b/core/java/com/android/internal/os/Zygote.java
@@ -211,6 +211,11 @@
      */
     native protected static void nativeUnmountStorageOnInit();
 
+    private static void callPostForkSystemServerHooks() {
+        // SystemServer specific post fork hooks run before child post fork hooks.
+        VM_HOOKS.postForkSystemServer();
+    }
+
     private static void callPostForkChildHooks(int runtimeFlags, boolean isSystemServer,
             boolean isZygote, String instructionSet) {
         VM_HOOKS.postForkChild(runtimeFlags, isSystemServer, isZygote, instructionSet);