[Darwin, testsuite] Remove unused test.

During GCC-9, the codegen for unreachable switch case statements changed
such that the (undefined) behaviour of reaching such statements is directed
to one of the existing switch cases.  This means that the testcase which
deals with the old behaviour can no longer work (and there is nothing to test
with it).  The [Darwin-specific] test is now redundant and can be removed.

gcc/testsuite/

2019-07-12  Iain Sandoe  <iain@sandoe.co.uk>

	* gcc.dg/pr57438-2.c: Remove.

From-SVN: r273457

gcc/testsuite/ChangeLog

+2019-07-12  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* gcc.dg/pr57438-2.c: Remove.
+
 2019-07-12  Martin Sebor  <msebor@redhat.com>
 
 	* gcc.dg/Warray-bounds-43.c: New test.

gcc/testsuite/gcc.dg/pr57438-2.c

-/* { dg-do compile { target *-*-darwin* } } */
-/* { dg-options "--param case-values-threshold=3 -O2" } */
-/* { dg-additional-options "-funwind-tables" { target powerpc*-*-darwin* } }
-
-/* This is testing that a trailing local label is followed by a
-   nop where required.  */
-   
-int foo (int x)
-{
-  switch (x)
-    {
-      case 0:
-        return 10;
-      case 3:
-        return -1;
-      case 5:
-        return 29;
-      default:
-        __builtin_unreachable();
-    }
-}
-
-/* { dg-final { scan-assembler "nop\\nLFE.*" { target  { *-*-darwin* } } } } */