Add another work-around for CCE.

* Apparently craycc also makes some optimistic assumptions about the effect
  of comparing -0.0 to 0.0.

tests/simple_model_helper.h

@@ -24,7 +24,11 @@ var_scale(int datatype, double *mscale, double *mrscale);
 static inline double
 sign_flat(double v)
 {
+#ifdef _CRAYC
+  if (v == 0 && copysign(1.0, v) < 0.0) return 0.0;
+#else
   if (!(v < 0.0 || v > 0.0)) return 0.0;
+#endif
   //    if (v == 0.0) return 0.0;
   return v;
 }