Fix arm macro, __arm__ is only defined for 32 bit arm

cpp/mrc/src/tests/test_pipeline.cpp

@@ -510,7 +510,7 @@ TEST_F(TestPipeline, Nodes1k)
 
 TEST_F(TestPipeline, EngineFactories)
 {
-#if defined(__arm__)
+#if defined(__aarch64__)
     GTEST_SKIP() << "Skipping test for arm architectures ref: https://github.com/nv-morpheus/MRC/issues/525";
 #endif
     auto topology = mrc::system::Topology::Create();