Add support for x86 VirtualBox Emulation

To make a VirtualBox install image,
  make installer_img
diff --git a/target/board/generic_x86/AndroidBoard.mk b/target/board/generic_x86/AndroidBoard.mk
index 9d64d52..ff46149 100644
--- a/target/board/generic_x86/AndroidBoard.mk
+++ b/target/board/generic_x86/AndroidBoard.mk
@@ -6,3 +6,12 @@
 LOCAL_MODULE_CLASS := SHARED_LIBRARIES
 LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT)
 include $(BUILD_PREBUILT)
+
+ifeq ($(TARGET_PREBUILT_KERNEL),)
+LOCAL_KERNEL := prebuilt/android-x86/kernel/kernel
+else
+LOCAL_KERNEL := $(TARGET_PREBUILT_KERNEL)
+endif
+
+PRODUCT_COPY_FILES += \
+    $(LOCAL_KERNEL):kernel