M README.md → README.md

@@ -96,9 +96,15 @@ This will build and install mGBA into `/usr/bin` and `/usr/lib`. Dependencies that are installed will be automatically detected, and features that are disabled if the dependencies are not found will be shown after running the `cmake` command after warnings about being unable to find them.
 
 #### Windows developer building
 
-To build on Windows for development, using MSYS2 is recommended. Follow the installation steps found on their [website](https://msys2.github.io). Make sure you're running the 32-bit version ("MinGW-w64 Win32 Shell") and run this additional command (including the braces) to install the needed dependencies (please note that this involves downloading over 500MiB of packages, so it will take a long time):
+To build on Windows for development, using MSYS2 is recommended. Follow the installation steps found on their [website](https://msys2.github.io). Make sure you're running the 32-bit version ("MinGW-w64 Win32 Shell") (or the 64-bit version "MinGW-w64 Win64 Shell" if you want to build for x86_64) and run this additional command (including the braces) to install the needed dependencies (please note that this involves downloading over 500MiB of packages, so it will take a long time):
 
+For x86 (32 bit) builds:
+
 	pacman -Sy mingw-w64-i686-{cmake,ffmpeg,gcc,gdb,imagemagick,libzip,pkg-config,qt5,SDL2}
+
+For x86_64 (64 bit) builds:
+
+	pacman -Sy mingw-w64-x86_64-{cmake,ffmpeg,gcc,gdb,imagemagick,libzip,pkg-config,qt5,SDL2}
 
 Check out the source code by running this command:
 
@@ -112,7 +118,7 @@ cd build
 	cmake .. -G "MSYS Makefiles"
 	make
 
-Please note that this build of mGBA for Windows is not suitable for distribution, due to the scattering of DLLs it needs to run, but is perfect for development.
+Please note that this build of mGBA for Windows is not suitable for distribution, due to the scattering of DLLs it needs to run, but is perfect for development. However, if distributing such a build is desired (e.g. for testing on machines that don't have the MSYS2 environment installed), a tool called "[Dependency Walker](http://dependencywalker.com)" can be used to see which additional DLL files need to be shipped with the mGBA executable.
 
 ### Dependencies