core: Introduce a pvmfwimage phony target

Similarly to other images, introduce a Ximage phony target for building
the pvmfw.img partition image.

Bug: 237371962
Test: m pvmfwimage
Change-Id: I2c17ec93c1e00d4d4df6f5196333ccb73a7c56d2
diff --git a/core/Makefile b/core/Makefile
index 47d06cc..0accfb6 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -3907,6 +3907,10 @@
 # -----------------------------------------------------------------
 # Protected VM firmware image
 ifeq ($(BOARD_USES_PVMFWIMAGE),true)
+
+.PHONY: pvmfwimage
+pvmfwimage: $(INSTALLED_PVMFWIMAGE_TARGET)
+
 INSTALLED_PVMFWIMAGE_TARGET := $(PRODUCT_OUT)/pvmfw.img
 INSTALLED_PVMFW_EMBEDDED_AVBKEY_TARGET := $(PRODUCT_OUT)/pvmfw_embedded.avbpubkey
 PREBUILT_PVMFWIMAGE_TARGET := packages/modules/Virtualization/pvmfw/pvmfw.img