Make compiler/utils/ symbols hidden.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: I5e39375f16e0ff1372c35fda444a4ef33bf320bf
diff --git a/compiler/utils/jni_macro_assembler_test.h b/compiler/utils/jni_macro_assembler_test.h
index 62e8191..ac8e7d3 100644
--- a/compiler/utils/jni_macro_assembler_test.h
+++ b/compiler/utils/jni_macro_assembler_test.h
@@ -20,6 +20,7 @@
 #include "jni_macro_assembler.h"
 
 #include "assembler_test_base.h"
+#include "base/macros.h"
 #include "base/malloc_arena_pool.h"
 #include "common_runtime_test.h"  // For ScratchFile
 
@@ -30,7 +31,7 @@
 #include <fstream>
 #include <iterator>
 
-namespace art {
+namespace art HIDDEN {
 
 template<typename Ass>
 class JNIMacroAssemblerTest : public AssemblerTestBase {