Remove static inline which is C++ 17

Author: ThomsonTan

sdk/include/opentelemetry/sdk/metrics/state/async_metric_storage.h

@@ -43,7 +43,7 @@ class AsyncMetricStorage : public MetricStorage, public AsyncWritableMetricStora
                      const AggregationConfig *aggregation_config)
       : instrument_descriptor_(instrument_descriptor),
         aggregation_type_{aggregation_type},
-        aggregation_config_{aggregation_config ? aggregation_config : &default_aggregation_config_},
+        aggregation_config_{aggregation_config ? aggregation_config : &GetDefaultAggregationConfig()},
         cumulative_hash_map_(
             std::make_unique<AttributesHashMap>(aggregation_config_->cardinality_limit_)),
         delta_hash_map_(
@@ -139,7 +139,10 @@ class AsyncMetricStorage : public MetricStorage, public AsyncWritableMetricStora
   }
 
 private:
-  static inline const AggregationConfig default_aggregation_config_{};
+  static const AggregationConfig& GetDefaultAggregationConfig() {
+    static const AggregationConfig default_config{};
+    return default_config;
+  }
   InstrumentDescriptor instrument_descriptor_;
   AggregationType aggregation_type_;
   const AggregationConfig *aggregation_config_;

sdk/include/opentelemetry/sdk/metrics/state/sync_metric_storage.h

@@ -66,7 +66,7 @@ class SyncMetricStorage : public MetricStorage, public SyncWritableMetricStorage
 #endif
                     const AggregationConfig *aggregation_config)
       : instrument_descriptor_(instrument_descriptor),
-        aggregation_config_(aggregation_config ? aggregation_config : &default_aggregation_config_),
+        aggregation_config_(aggregation_config ? aggregation_config : &GetDefaultAggregationConfig()),
         attributes_hashmap_(
             std::make_unique<AttributesHashMap>(aggregation_config_->cardinality_limit_)),
         attributes_processor_(std::move(attributes_processor)),
@@ -173,7 +173,10 @@ class SyncMetricStorage : public MetricStorage, public SyncWritableMetricStorage
                nostd::function_ref<bool(MetricData)> callback) noexcept override;
 
 private:
-  static inline const AggregationConfig default_aggregation_config_{};
+  static const AggregationConfig& GetDefaultAggregationConfig() {
+    static const AggregationConfig default_config{};
+    return default_config;
+  }
   InstrumentDescriptor instrument_descriptor_;
   // hashmap to maintain the metrics for delta collection (i.e, collection since last Collect call)
   const AggregationConfig *aggregation_config_;