DUChainReferenceCounting: use instance function to acquire instance

Windows doesn't support dllexport with thread_local
1 job for !198 with DUChainReferenceCounting__instance in 32 minutes and 47 seconds (queued for 14 minutes and 46 seconds)
latest detached
Status Job ID Name Coverage
  Build
passed #80318
linux kf5-qt5 qt5.12

00:32:47

47.0%