Add another testcase for PR 110266

Since the combining of sin/cos into cexpi is depedent
on the target, this adds another testcase which had failed (earlier in
evpr rather than vrp2) that will fail on all targets rather than
ones which have sincos or C99 math functions.

Committed as obvious after a quick test.

gcc/testsuite/ChangeLog:

	PR tree-optimization/110266
	* gcc.c-torture/compile/pr110266.c: New test.

gcc/testsuite/gcc.c-torture/compile/pr110266.c

@@ -0,0 +1,9 @@
+double PsyBufferUpdate(int n)
+{
+  if (n == 4)
+    {
+      _Complex double t = __builtin_cexpi(n);
+      return __real t * __imag t;
+    }
+  return 0;
+}