Stop using the files target for droidcore

This way if a BoardConfig.mk configures a specific image to exist (so it
doesn't end up as a folder on /system), but does not configure for it to
be created (like the device targets on AOSP that use a prebuilt), we
won't unnecessarily trigger the build system to build the contents.

Test: `m` before and after, comparing file lists
Test: check treehugger builds before/after
Change-Id: If0e4b958b3dfaa02771a5da70f970379635f904e

core/main.mk

@@ -1305,8 +1305,8 @@ auxiliary: $(INSTALLED_AUX_TARGETS)
 
 # Build files and then package it into the rom formats
 .PHONY: droidcore
-droidcore: files \
-    systemimage \
+droidcore: $(filter $(HOST_OUT_ROOT)/%,$(modules_to_install)) \
+    $(INSTALLED_SYSTEMIMAGE_TARGET) \
     $(INSTALLED_RAMDISK_TARGET) \
     $(INSTALLED_BOOTIMAGE_TARGET) \
     $(INSTALLED_RECOVERYIMAGE_TARGET) \
@@ -1337,6 +1337,7 @@ droidcore: files \
     $(INSTALLED_FILES_JSON_ROOT) \
     $(INSTALLED_FILES_FILE_RECOVERY) \
     $(INSTALLED_FILES_JSON_RECOVERY) \
+    $(INSTALLED_ANDROID_INFO_TXT_TARGET) \
     soong_docs
 
 # dist_files only for putting your library into the dist directory with a full build.

core/tasks/module-info.mk

@@ -25,7 +25,7 @@ $(MODULE_INFO_JSON):
 # If ONE_SHOT_MAKEFILE is set, our view of the world is smaller, so don't
 # rewrite the file in that came.
 ifndef ONE_SHOT_MAKEFILE
-files: $(MODULE_INFO_JSON)
+droidcore: $(MODULE_INFO_JSON)
 endif
 
 $(call dist-for-goals, general-tests, $(MODULE_INFO_JSON))