try non-inline variable

Author: nathanhhughes

.github/workflows/ci.yaml

@@ -1,7 +1,7 @@
 ---
 # based on https://github.com/actions/starter-workflows/blob/main/ci/cmake-single-platform.yml
 name: 'Spark-DSG Build and Test'
-on: [pull_request]
+on: [pull_request, {push: {branches: [fix/cross_platform]}}]
 jobs:
   lint:
     runs-on: ubuntu-latest

include/spark_dsg/serialization/attribute_serialization.h

@@ -131,7 +131,7 @@ class Visitor {
   } type_;
 
   std::unique_ptr<SerializationImpl> impl_;
-  inline thread_local static std::unique_ptr<Visitor> s_instance_ = nullptr;
+  thread_local static std::unique_ptr<Visitor> s_instance_;
 };
 
 template <typename T>

src/serialization/attribute_serialization.cpp

@@ -36,6 +36,8 @@
 
 namespace spark_dsg::serialization {
 
+std::unique_ptr<Visitor> Visitor::s_instance_ = nullptr;
+
 Visitor& Visitor::instance() {
   if (!s_instance_) {
     s_instance_.reset(new Visitor());