Suppress clang-tidy performance warnings in libmemunreachable.

Bug: 30413862
Change-Id: If3ed64d2e1ca1f46599de9fe97c769f468ee1a68
Test: build with WITH_TIDY=1
diff --git a/libmemunreachable/tests/Allocator_test.cpp b/libmemunreachable/tests/Allocator_test.cpp
index fa76ae0..21c8218 100644
--- a/libmemunreachable/tests/Allocator_test.cpp
+++ b/libmemunreachable/tests/Allocator_test.cpp
@@ -160,7 +160,7 @@
 
   Allocator<int>::shared_ptr ptr = allocator.make_shared(0);
   {
-    auto ptr2 = ptr;
+    auto ptr2 = ptr;  // NOLINT, test copy of ptr
   }
   ASSERT_NE(ptr, nullptr);
 }