Add instructions for building the sources.

README.md

@@ -16,3 +16,13 @@ Extract takes a decrypted IPF as argument and generates a list of files.
 Some extension files aren't decrypted entirely ; In that case, only the MD5 of the decrypted is generated.
 
 ![HowTo](http://i.imgur.com/UJzXDZN.gif)
+
+
+### Build the sources
+
+If you want to build IPFUnpacker, I suggest using GCC - The code is compilable both under Windows and Linux.
+Here is a quick guide how to compile the sources on Windows : 
+- Download MSYS2 (http://sourceforge.net/projects/msys2/files/latest/download)
+- Open the mingw64_shell.bat in the MSYS2 installation folder
+- Launch the command "pacman -S gcc make zlib-devel"
+- You should now be able to compile the code using "make clean && make release" next to the Makefile in the root folder.