support emsdk >3.1.51

since #2596 static.c build was silently ignored (commented by setuptools) because PNG/JPEG not set anymore in Setup

Author: pmp-p

buildconfig/Setup.Emscripten.SDL2.in

@@ -6,7 +6,8 @@
 #MIXER = -lSDL2_mixer
 #SCRAP =
 #FREETYPE = -lfreetype -lharfbuzz
-
+PNG = -lpng
+JPEG = -ljpeg
 DEBUG =
 
 # these can build alone and object files merged with ar