Bump libpng version

Author: MoNTE48

libpng.sh

@@ -1,7 +1,7 @@
 #!/bin/bash -e
 
 . ./sdk.sh
-PNG_VERSION=1.6.53
+PNG_VERSION=1.6.54
 
 mkdir -p output/libpng/lib/$TARGET_ABI
 mkdir -p deps; cd deps