if you try to make install on msys (potentially cygwin as well), it will fail installing libpng.dll
reason being it expects a symlink to libpng16.dll to have been created
there's an if statement on the create_symlink macro that goes like this
if(WIN32 AND NOT CYGWIN AND NOT MSYS)
msys does support symlink (as in ln -s will make a copy of the file)
but cmake -E create_symlink won't actually do anything
i found a discussion on the mailing list about whether it should fail silently or loudly... and i guess it's still failing silently.
so i think that we need to change it so that it makes a copy under msys