diagnostics: Fix selftest ICE in certain locales [PR107722]

As reported in the PR, since special_fname_builtin () call has been
introduced, the diagnostics code compares filename against _("<built-in>")
rather than "<built-in>", which means that if self tests are performed
with the string being translated, one self-test fails.
The following patch fixes that.

2022-11-23  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/107722
	* diagnostic.cc (test_diagnostic_get_location_text): Test
	special_fname_builtin () rather than "<built-in>" and expect
	special_fname_builtin () concatenated with ":" for it.
diff --git a/gcc/diagnostic.cc b/gcc/diagnostic.cc
index 7c7ee6d..a9562a8 100644
--- a/gcc/diagnostic.cc
+++ b/gcc/diagnostic.cc
@@ -2593,7 +2593,10 @@
   const char *old_progname = progname;
   progname = "PROGNAME";
   assert_location_text ("PROGNAME:", NULL, 0, 0, true);
-  assert_location_text ("<built-in>:", "<built-in>", 42, 10, true);
+  char *built_in_colon = concat (special_fname_builtin (), ":", (char *) 0);
+  assert_location_text (built_in_colon, special_fname_builtin (),
+			42, 10, true);
+  free (built_in_colon);
   assert_location_text ("foo.c:42:10:", "foo.c", 42, 10, true);
   assert_location_text ("foo.c:42:9:", "foo.c", 42, 10, true, 0);
   assert_location_text ("foo.c:42:1010:", "foo.c", 42, 10, true, 1001);