utils: to_range(): relax constraint

The input range to utils::to_range() should be indeed a range,
but clang has trouble compiling <ranges> which causes it to fail.

Relax the constraint until this is fixed.

utils/ranges.hh

@@ -25,7 +25,13 @@
 
 namespace ranges {
 
+#ifndef __clang__
 template <std::ranges::range Container, std::ranges::range Range>
+#else
+// 'Range' should be constrained to std::ranges::range, but due to
+// problems between clang and <ranges>, it cannot be
+template <std::ranges::range Container, typename Range>
+#endif
 Container to(const Range& range) {
     return Container(range.begin(), range.end());
 }