Cheat a little by copying one specific file in allegro5, that is supposed to be internal-use only.

allegro5/Makefile

@@ -30,6 +30,8 @@ package:
 	rm -rf out
 	mkdir -p out/opt/cppse/build/allegro5/
 	cp -prv allegro5/allegro5_static/* out/opt/cppse/build/allegro5/
+	# with one exception I'm relying on internals of allegro5 for one file..
+	cp -prv allegro5/include/allegro5/internal/aintern_bitmap.h out/opt/cppse/build/allegro5/include/allegro5/internal/aintern_bitmap.h
 	rm -rf allegro5_1.0_amd64.deb
 	docker run -v "$$(pwd):/src/" rayburgemeestre/fpm-ubuntu:18.04 fpm -s dir -t deb -n allegro5 --license MPL2 --maintainer "Ray Burgemeestre <ray@cppse.nl>" --description "allegro5 - build dependency" --url "https://github.com/liballeg/allegro5.git" --deb-generate-changes -C /src/out