Add missing field init in constructors

Adds missing field initializations detected by Eclipse IDE.

Change-Id: I5f2f32bcccb12545fc9f0b42fcec74a23dc81376
diff --git a/compiler/optimizing/builder.h b/compiler/optimizing/builder.h
index 19dd944..d6b25ee 100644
--- a/compiler/optimizing/builder.h
+++ b/compiler/optimizing/builder.h
@@ -76,7 +76,8 @@
         code_start_(nullptr),
         latest_result_(nullptr),
         can_use_baseline_for_string_init_(true),
-        compilation_stats_(nullptr) {}
+        compilation_stats_(nullptr),
+        interpreter_metadata_(nullptr) {}
 
   bool BuildGraph(const DexFile::CodeItem& code);