Make compiler/debug/ symbols hidden.

And mark required symbols with EXPORT.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: I8efec9299bdd6becf625e7a59c75cbaf053eadb9
diff --git a/compiler/debug/method_debug_info.h b/compiler/debug/method_debug_info.h
index 152db6e..b83c6e2 100644
--- a/compiler/debug/method_debug_info.h
+++ b/compiler/debug/method_debug_info.h
@@ -21,9 +21,10 @@
 
 #include "arch/instruction_set.h"
 #include "base/array_ref.h"
+#include "base/macros.h"
 #include "dex/dex_file.h"
 
-namespace art {
+namespace art HIDDEN {
 namespace debug {
 
 struct MethodDebugInfo {