make tfragment_gc more robust for Appveyor
make tfragment_gc more robust for Appveyor

russpowers/Nim,dom96/Nim,russpowers/Nim,dom96/Nim,dom96/Nim,russpowers/Nim,dom96/Nim,russpowers/Nim,russpowers/Nim,dom96/Nim,russpowers/Nim,dom96/Nim,russpowers/Nim,dom96/Nim