[test] exercise breakLoopBackedge with a switch latch cond

This was reduced from a test case which triggered a revert to my recent change to same function.  It turns out we didn't have *any* coverage of the non-branch latch and my patch was blatantly broken.

llvm/test/Transforms/LoopDeletion/switch.ll

@@ -0,0 +1,43 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -loop-deletion -verify-loop-info -S | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+@G = external global i32
+
+define void @func_1() {
+; CHECK-LABEL: @func_1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LBL_2368:%.*]]
+; CHECK:       lbl_2368:
+; CHECK-NEXT:    [[CMP289:%.*]] = icmp slt i32 undef, -5
+; CHECK-NEXT:    br i1 [[CMP289]], label [[CLEANUP967:%.*]], label [[UNREACHABLE:%.*]]
+; CHECK:       cleanup967:
+; CHECK-NEXT:    switch i32 undef, label [[CLEANUP1169:%.*]] [
+; CHECK-NEXT:    i32 20, label [[CLEANUP967_LBL_2368_CRIT_EDGE:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       cleanup967.lbl_2368_crit_edge:
+; CHECK-NEXT:    unreachable
+; CHECK:       cleanup1169:
+; CHECK-NEXT:    ret void
+; CHECK:       unreachable:
+; CHECK-NEXT:    unreachable
+;
+entry:
+  br label %lbl_2368
+
+lbl_2368:
+  %cmp289 = icmp slt i32 undef, -5
+  br i1 %cmp289, label %cleanup967, label %unreachable
+
+cleanup967:
+  switch i32 undef, label %cleanup1169 [
+  i32 20, label %lbl_2368
+  ]
+
+cleanup1169:
+  ret void
+
+unreachable:
+  unreachable
+}