libstdc++: test for failing assertion should use 'run' not 'compile'

And it only needs to define _GLIBCXX_ASSERTIONS not _GLIBCXX_DEBUG.

	* testsuite/24_iterators/range_operations/advance_debug_neg.cc: Run
	test instead of just compiling it.

libstdc++-v3/ChangeLog

+2020-02-28  Jonathan Wakely  <jwakely@redhat.com>
+
+	* testsuite/24_iterators/range_operations/advance_debug_neg.cc: Run
+	test instead of just compiling it.
+
 2020-02-28  Patrick Palka  <ppalka@redhat.com>
 
 	* include/std/ranges (reverse_view::_S_needs_cached_begin): Set to false

libstdc++-v3/testsuite/24_iterators/range_operations/advance_debug_neg.cc

@@ -15,8 +15,9 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-options "-std=gnu++2a -D_GLIBCXX_DEBUG" }
-// { dg-do compile { xfail c++2a } }
+// { dg-options "-std=gnu++2a -D_GLIBCXX_ASSERTIONS" }
+// { dg-do run { xfail *-*-* } }
+// { dg-require-effective-target c++2a }
 
 #include <iterator>
 #include <testsuite_iterators.h>
@@ -29,3 +30,8 @@ test01()
   auto iter = c.begin();
   std::ranges::advance(iter, -1);
 }
+
+int main()
+{
+  test01();
+}