Fix aux_config warning

Don't declare targets during config files, as they're loaded in other
contexts as well. In this case, `droidcore` was not defined when we were
handling CleanSpec.mk files, leading to:

build/make/core/aux_config.mk:185: warning: real file "droidcore" depends on PHONY target "auxiliary"

Bug: 123583617
Test: m nothing; check for warnings
Change-Id: I71b8819deb81442810c7dd5c681ddb38a1171cff

core/aux_config.mk

@@ -181,5 +181,3 @@ $(foreach v,$(AUX_ALL_VARIANTS),\
 endif
 
 INSTALLED_AUX_TARGETS :=
-
-droidcore: auxiliary

core/main.mk

@@ -1388,6 +1388,7 @@ droidcore: $(filter $(HOST_OUT_ROOT)/%,$(modules_to_install)) \
     $(INSTALLED_FILES_FILE_RECOVERY) \
     $(INSTALLED_FILES_JSON_RECOVERY) \
     $(INSTALLED_ANDROID_INFO_TXT_TARGET) \
+    auxiliary \
     soong_docs
 
 # dist_files only for putting your library into the dist directory with a full build.