Same problem here... app built on Ubuntu16.04 LTS doesn't run on newest 17 version.
I did a text search for STATIC_PNG in whole UPP tree, no traces of it, so the reported solution must be wrong.
I tried to remove png lib from plugins/png package and add it as static lib, but I got just errors.

Is there a way to force static linking of PNG library ?
I remember I did it with ssl library as above, and it worked. With PNG no way up to now.

Ciao

Massimo