There is an
overview of command lines/switches for dub.
Dmd as well as Ldc seem to try to build the 64bit build on Windows by default. The switch to affect that is '--arch=...', for 32bit build '...' is 'x86' ('x86_64' for 64bit build).
For the choice of compiler you can use the switch '--compiler=...', if you want sth different from what is used by default. Lix supports 'dmd' and 'ldc2' for '...' . (At least on Windows only 64bit is supported with ldc2 and 32bit with dmd, 64bit with dmd is supported
with some tweaks).
If you look closely it tells you for what architecture which compiler is building, at the beginning there is e.g. the line 'Performing "debug" build using C:\D\ldc2\bin\ldc2.exe for x86_64'.
