Make compiler/jni/ symbols hidden.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: I04dc99e1491219442ba128f57a08112ae4783b92
diff --git a/compiler/jni/quick/jni_compiler.h b/compiler/jni/quick/jni_compiler.h
index 52a6f3c..d43b2a9 100644
--- a/compiler/jni/quick/jni_compiler.h
+++ b/compiler/jni/quick/jni_compiler.h
@@ -21,8 +21,9 @@
 
 #include "arch/instruction_set.h"
 #include "base/array_ref.h"
+#include "base/macros.h"
 
-namespace art {
+namespace art HIDDEN {
 
 class ArenaAllocator;
 class ArtMethod;