Windows: install step installs in C:\

[nidefawl]

Right now the install step on windows copies files to the root of your file system.

CMAKE_INSTALL_PREFIX is ignored for all files but the lib. That is because CMAKE_INSTALL_* variables are empty.

This has to do with: https://github.com/mborgerding/kissfft/blob/8f47a67f595a6641c566087bf5277034be64f24d/CMakeLists.txt#L104-L110

GNUInstallDirs should be included unconditionally. That is what most projects do. See glfw, portaudio, SQLiteCPP.

Otherwise one cannot use the install step on windows.