Add soong_docs to droidcore

Bug: 70516282
Test: treehugger
Change-Id: I818ad6f948502f4beb0205b583687c1d9fa563ac
diff --git a/core/main.mk b/core/main.mk
index cac9c59..621d309 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -1052,7 +1052,8 @@
 	$(INSTALLED_SYSTEMOTHERIMAGE_TARGET) \
 	$(INSTALLED_FILES_FILE) \
 	$(INSTALLED_FILES_FILE_VENDOR) \
-	$(INSTALLED_FILES_FILE_SYSTEMOTHER)
+	$(INSTALLED_FILES_FILE_SYSTEMOTHER) \
+	soong_docs
 
 # dist_files only for putting your library into the dist directory with a full build.
 .PHONY: dist_files