So I’m working with Qt5 on Windows and figured that since the Qt5 SDK is currently only compiled against Visual Studio 2010, I had to figure out how to build the Botan library without using MinGW.
The build instructions for Botan are mostly complete, but lacks one vital step, namely calling the vcvarsall.bat script. This is found in the Visual Studio 2010 install directory, under the subdirectory VC. Just call this on the command prompt before doing anything else and your path and library variables will be set up properly.
After running this, you only need to follow the steps for building on Windows by configuring the build for MSVC, which you find over at Botan’s homepage.