User interface > Translation options > Target options > Target platform
At the target options you can chose the target platform.
The alternative platforms are: Window, Linux or MacIOS. The selected platform makes no big difference in the generated C++ code, because Delphi2Cpp aims to generate portable C++ code. But nevertheless some types are functions might be named differently for different platform. The source code for other compilers contains different conditions for the three platforms.
More important is the 64 Bit option. Depending on the chosen option some values in the type-map are different.
Delphi2CB only supports Windows as target platform