c++: add fixed test [PR39057]

This was fixed by r16-6725 and we no longer crash.  The error is
expected.

	PR c++/39057

gcc/testsuite/ChangeLog:

	* g++.dg/template/friend89.C: New test.

gcc/testsuite/g++.dg/template/friend89.C

@@ -0,0 +1,11 @@
+// PR c++/39057
+
+struct A
+{
+  template<int> void foo();
+};
+
+template<int> struct B
+{
+  friend void A::foo<0>(int = 0); // { dg-error "friend declaration" }
+};