Make cfgfile depth calculation thread friendly

src/config.cpp

@@ -46,6 +46,8 @@ constexpr static const char CACHE_FILES_PROCESS_NAMES_DEFAULT[] =
 
 Config cfg;
 
+thread_local int Config::CfgConfigFile::_depth = 0;
+
 Config::CfgConfigFile::CfgConfigFile()
 {
 }

src/config.hpp

@@ -95,7 +95,7 @@ public:
   {
   private:
     fs::path  _cfg_file;
-    int       _depth = 0;
+    static thread_local int _depth;
 
   public:
     CfgConfigFile();