Pass linker patches around as const.

Change-Id: I0eabd713d29475db9eb6e186f331dbfb00e0cf6b
diff --git a/compiler/linker/relative_patcher_test.h b/compiler/linker/relative_patcher_test.h
index 08167b3..70630f3 100644
--- a/compiler/linker/relative_patcher_test.h
+++ b/compiler/linker/relative_patcher_test.h
@@ -69,7 +69,7 @@
 
   void AddCompiledMethod(MethodReference method_ref,
                          const ArrayRef<const uint8_t>& code,
-                         const ArrayRef<LinkerPatch>& patches) {
+                         const ArrayRef<const LinkerPatch>& patches) {
     compiled_method_refs_.push_back(method_ref);
     compiled_methods_.emplace_back(new CompiledMethod(
         &driver_, instruction_set_, code,