#775 Linking dbghelp imports all unused API

[Rokas Kupstys]

Linking dbghelp library for some reason imports all of the exported functions even if they are not used. This also includes MapDebugInformation which no dbghelp.dll on test system (Windows 10 LTSB) export. As a result compiled application fails to start due to missing import.

Documentation indicates that my mentioned function should exist, and yet it does not on my system. I assume it could exist in some cases but not in others. As far as i understand issue would be fixed if compiler did not import unused API.

Tested with latest mingw-w64 distribution from msys2.