Add a check for apex/allowed_deps.txt to droidcore.

The check ensures that build graph for updatable modules contains only
allowed dependencies at build time.

Bug: 149622332
Test: m
Change-Id: I52a4be72efaa523d53827dd11822a7802543dd10
Merged-In: I5695dd1003386191dbbe0ea511ef5b615d0d5e4e
Exempt-From-Owner-Approval: cp

core/main.mk

@@ -1850,6 +1850,11 @@ tidy_only:
 ndk: $(SOONG_OUT_DIR)/ndk.timestamp
 .PHONY: ndk
 
+# Checks that build/soong/apex/allowed_deps.txt remains up to date
+ifneq ($(UNSAFE_DISABLE_APEX_ALLOWED_DEPS_CHECK),true)
+  droidcore: ${APEX_ALLOWED_DEPS_CHECK}
+endif
+
 $(call dist-write-file,$(KATI_PACKAGE_MK_DIR)/dist.mk)
 
 $(info [$(call inc_and_print,subdir_makefiles_inc)/$(subdir_makefiles_total)] writing build rules ...)