Stating with RubyInstaller-2.4 we're no longer using our own DevKit compilation, but make use of MSYS2 for both building Ruby itself as well as building Ruby gems with C-extensions. It can be installed by using RubyInstaller with Devkit or through the ridk install command, which is part of RubyInstaller-2.4+. Alternatively a manual download and installation from MSYS2 is also possible.

In order to enable compiler and typical Unix commands on the command line, type ridk enable. This makes MSYS2 tools "gcc", "make", etc. available in the PATH.

Alternatively rake can be started by something like this, to enable MSYS2 tools for the single command only:

rake -rdevkit test