DO NOT MERGE Update libpng to 1.6.20

BUG:23265085
Change-Id: I85199805636d771f3597b691b63bc0bf46084833
(cherry picked from commit bbe98b40cda082024b669fa508931042eed18f82)
diff --git a/scripts/makefile.32sunu b/scripts/makefile.32sunu
index c6e7fed..7d4b7c5 100644
--- a/scripts/makefile.32sunu
+++ b/scripts/makefile.32sunu
@@ -107,8 +107,8 @@
 	echo I_opts=\"-I$(INCPATH)/$(LIBNAME)\"; \
 	echo L_opts=\"-L$(LIBPATH)\"; \
 	echo R_opts=\"-R$(LIBPATH)\"; \
-	echo ccopts=\"-xtarget=ultra\"; \
-	echo ldopts=\"-xtarget=ultra\"; \
+	echo ccopts=\"-fast -xtarget=ultra\"; \
+	echo ldopts=\"-fast -xtarget=ultra\"; \
 	echo libs=\"-lpng16 -lz -lm\"; \
 	cat scripts/libpng-config-body.in ) > libpng-config
 	chmod +x libpng-config