PNG flags were accidentally included by gdk-pixbuf. This has been fixed
recently, so we need to make sure to include it ourselves.
AM_CFLAGS = @OPENMP_CFLAGS@
AM_LDFLAGS = @OPENMP_CFLAGS@
-LDADD = $(top_builddir)/pixman/libpixman-1.la -lm $(GTK_LIBS)
-INCLUDES = -I$(top_srcdir)/pixman -I$(top_builddir)/pixman $(GTK_CFLAGS)
+LDADD = $(top_builddir)/pixman/libpixman-1.la -lm $(GTK_LIBS) $(PNG_LIBS)
+INCLUDES = -I$(top_srcdir)/pixman -I$(top_builddir)/pixman $(GTK_CFLAGS) $(PNG_CFLAGS)
GTK_UTILS = gtk-utils.c gtk-utils.h