You need to iterate through each dependent DLL using objdump to get the full list. This is automated in pp_simple and pp_autolink, so perhaps give them a try.
FWIW, I get this set on Strawberry Perl 5.28 for a script that just does use GD; print "1";.
This is similar to the set provided by haj in 11117362 but missing libgraphite and libharfbuzz, presumably because I used a simpler script.
Update: I see marto has already provided links to pp_simple and pp_autolink info in 11117346.