makeMultiVal: use size of isl::multi_val

This avoids the use of a function in the C++ interface that
will not be exported in mainline isl.

Author: Sven Verdoolaege

tc/external/detail/islpp.h

@@ -292,7 +292,7 @@ inline isl::space addRange(isl::space space, unsigned dim) {
 template <typename T>
 isl::multi_val makeMultiVal(isl::space s, const std::vector<T>& vals) {
   isl::multi_val mv = isl::multi_val::zero(s);
-  TC_CHECK_EQ(vals.size(), s.dim(isl::dim_type::set));
+  TC_CHECK_EQ(vals.size(), static_cast<size_t>(mv.size()));
   for (size_t i = 0; i < vals.size(); ++i) {
     mv = mv.set_val(i, isl::val(s.get_ctx(), vals[i]));
   }