Fix '--as-needed' build for zmf with system libpng

Change-Id: I92378dae4a515a587c897fff83b15d8e836b0aa2
Reviewed-on: https://gerrit.libreoffice.org/28974
Tested-by: Jenkins <[email protected]>
Reviewed-by: Jan-Marek Glogowski <[email protected]>
diff --git a/writerperfect/Library_wpftdraw.mk b/writerperfect/Library_wpftdraw.mk
index ec9057c..cff3090 100644
--- a/writerperfect/Library_wpftdraw.mk
+++ b/writerperfect/Library_wpftdraw.mk
@@ -50,6 +50,7 @@ $(eval $(call gb_Library_use_externals,wpftdraw,\
	mspub \
	mwaw \
	odfgen \
	zmf \
	png \
	pagemaker \
	revenge \
@@ -58,7 +59,6 @@ $(eval $(call gb_Library_use_externals,wpftdraw,\
	wpg \
	wpd \
	zlib \
	zmf \
	lcms2 \
	libxml2 \
	icui18n \