Fixes compilation error "ResourceSet.h:33:21: error: function 'ResourceSet::ResourceSet()' definition is marked dllimport" when building with g++ 12.1.0

lib/ResourceSet.cpp

@@ -19,6 +19,8 @@
 
 VCMI_LIB_NAMESPACE_BEGIN
 
+ResourceSet::ResourceSet() = default;
+
 ResourceSet::ResourceSet(const JsonNode & node)
 {
 	for(auto i = 0; i < GameConstants::RESOURCE_QUANTITY; i++)

lib/ResourceSet.h

@@ -30,7 +30,7 @@ private:
 public:
 	// read resources set from json. Format example: { "gold": 500, "wood":5 }
 	DLL_LINKAGE ResourceSet(const JsonNode & node);
-	DLL_LINKAGE ResourceSet() = default;
+	DLL_LINKAGE ResourceSet();
 
 
 #define scalarOperator(OPSIGN)									\