odrefresh: Avoid uninitialized usage

compilation_os_mode_ was only getting set when
SetCompilationOsMode() was called.  We initialize it to make sure
we have a consistent value if that function isn't called.

Test: TreeHugger
Bug: 211458160
Change-Id: Ic743969d3d0153561211a69eb32d5509e1c83cca
diff --git a/odrefresh/odr_config.h b/odrefresh/odr_config.h
index 9a8b6ba..f5676e1 100644
--- a/odrefresh/odr_config.h
+++ b/odrefresh/odr_config.h
@@ -71,7 +71,7 @@
   time_t max_execution_seconds_ = kMaximumExecutionSeconds;
   time_t max_child_process_seconds_ = kMaxChildProcessSeconds;
   std::string standalone_system_server_jars_;
-  bool compilation_os_mode_;
+  bool compilation_os_mode_ = false;
 
   // Staging directory for artifacts. The directory must exist and will be automatically removed
   // after compilation. If empty, use the default directory.