Reduce the scope of a ScopedObjectAccess in dex2oat.

Allow concurrent GCs during image writing, etc.

Change-Id: I89b70a6dfb17f58b156e164c91457337f1c2648f
diff --git a/compiler/oat_writer.h b/compiler/oat_writer.h
index f7801f5..8111c9f 100644
--- a/compiler/oat_writer.h
+++ b/compiler/oat_writer.h
@@ -66,7 +66,7 @@
             uint32_t image_file_location_oat_checksum,
             uint32_t image_file_location_oat_begin,
             const std::string& image_file_location,
-            const CompilerDriver* compiler) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+            const CompilerDriver* compiler);
 
   const OatHeader& GetOatHeader() const {
     return *oat_header_;