Invoke make package for png++ and seasocks.

png++/Makefile

 pngpp:
 	wget http://download.savannah.nongnu.org/releases/pngpp/png++-0.2.9.tar.gz
 	tar -zxvf png++-0.2.9.tar.gz
+	make package
 
 package:
 	rm -rf out

seasocks/Makefile

 seasocks_:
 	git clone https://github.com/rayburgemeestre/seasocks --branch v1.4.3
 	bash ../ubuntu1804.sh make impl
-	# make package
+	make package
 
 impl:
 	update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++-10 40