core/Makefile: Add desktop pack image hook.

Desktop currently has a custom pack image script that is valuable
to run in pre/post-submit builders. Add hook to the core Makefile
to allow running it.

Bug: b:349581445
Test: m
Change-Id: I368d3c8278beeee9f5c3e863043869c18e773728
diff --git a/core/Makefile b/core/Makefile
index b76a4f8..b3e84c9 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -7851,6 +7851,29 @@
 # Extract platform fonts used in Layoutlib
 include $(BUILD_SYSTEM)/layoutlib_data.mk
 
+# -----------------------------------------------------------------
+# Desktop pack image hook.
+ifneq (,$(strip $(PACK_DESKTOP_FILESYSTEM_IMAGES)))
+PACK_IMAGE_TARGET := $(PRODUCT_OUT)/android-desktop_image.bin
+PACK_IMAGE_SCRIPT := $(HOST_OUT_EXECUTABLES)/pack_image
+IMAGES := $(INSTALLED_BOOTIMAGE_TARGET) \
+	$(INSTALLED_SUPERIMAGE_TARGET) \
+	$(INSTALLED_INIT_BOOT_IMAGE_TARGET) \
+	$(INSTALLED_VENDOR_BOOTIMAGE_TARGET) \
+	$(INSTALLED_VBMETAIMAGE_TARGET) \
+	$(INSTALLED_USERDATAIMAGE_TARGET)
+
+$(PACK_IMAGE_TARGET): $(IMAGES) $(PACK_IMAGE_SCRIPT)
+	$(PACK_IMAGE_SCRIPT) --out_dir $(PRODUCT_OUT) --noarchive
+
+PACKED_IMAGE_ARCHIVE_TARGET := $(PACK_IMAGE_TARGET).gz
+
+$(PACKED_IMAGE_ARCHIVE_TARGET): $(PACK_IMAGE_TARGET) | $(GZIP)
+	$(GZIP) -fk $(PACK_IMAGE_TARGET)
+
+droidcore-unbundled: $(PACKED_IMAGE_ARCHIVE_TARGET)
+
+endif # PACK_DESKTOP_FILESYSTEM_IMAGES
 
 # -----------------------------------------------------------------
 # OS Licensing