Fix: correctly destruct VIXL labels.

Bug: 27505766
Change-Id: I077465e3d308f4331e7a861902e05865f9d99835
diff --git a/compiler/optimizing/code_generator.cc b/compiler/optimizing/code_generator.cc
index a771cc1..e7fa4e4 100644
--- a/compiler/optimizing/code_generator.cc
+++ b/compiler/optimizing/code_generator.cc
@@ -187,7 +187,8 @@
 
 void CodeGenerator::GenerateSlowPaths() {
   size_t code_start = 0;
-  for (SlowPathCode* slow_path : slow_paths_) {
+  for (const std::unique_ptr<SlowPathCode>& slow_path_unique_ptr : slow_paths_) {
+    SlowPathCode* slow_path = slow_path_unique_ptr.get();
     current_slow_path_ = slow_path;
     if (disasm_info_ != nullptr) {
       code_start = GetAssembler()->CodeSize();