Okay heres a quick guide I've just made on how to compile ReiNand in Windows 8/10.
Download the following files:
GitHub
devkitPro
Python
gcc-arm-none-eab
MinGW-get-setup
firmware.bin & armips.exe (Linked on the Git).
Install GitHub.
Install devkitPro.
Install Python.
Install gcc-arm-none-eab (At the end of setup make sure you tick the 'Environmental Variables' option).
Install MinGW-get-setup, open the MinGw Installer and select 'mingw-developer-toolkit'. Then select Installation and Apply Changes.
Copy armips.exe to it's own folder (e.g. 'C:\CommandPrograms').
Navigate to Control Panel/System/Advanced System Settings/Environmental Variables.
You will see two boxes. One labelled 'User Variables' and the other 'System Variables'. DO NOT TOUCH ANYTHING IN SYSTEM VARIABLES!
Under 'User Variables', edit the variable called 'PATH' (create it if it's not there) and ADD armips, Python and the MinGW bin directories to the list, separating each directory with a ';'.
(Default is 'C:\MinGW\bin;C:\MinGW\msys\1.0\bin;C:\CommandPrograms;C:\Python34;').
(NOTE: If GNU Tools isn't mentioned at all in your PATH, then you must have missed the tick box earlier when installing the program. If this is the case; just add the bin folder of the location it's installed in to the list. E.g. 'C:\Program Files (x86)\GNU Tools ARM Embedded\4.9 2015q2\bin;').
Click OK to save the changes.
In Git Shell, type in 'git clone --recursive
https://github.com/Reisyukaku/ReiNand.git'. This will add ReiNand source to your GitHub directory.
Copy the firmware.bin file into the ReiNand\data directory.
(For some reason if I try to build ReiNand in Git Shell, it crashes on my system. Not sure if this is Windows 10 related, but for the rest of the tutorial I used the normal command prompt).
Type in 'cd (wherever ReiNand is)'.
Type in 'make'.
As long as this was successful, it should compile the source code to the ReiNand\Out directory.
Enjoy, and thanks to Reisyukaku for providing the source code!