2. Disable autocrlf for ffmpeg, as its build system manages to not support Windows newlines: `cd vendor/ffmpeg && git config --local core.autocrlf && git rm --cached -r . && git reset --hard`
3. Open Visual Studio from the VS2013 Native Tools Command Promp using devenv.exe /useenv (required for the build system to be able to find nmake.exe for building wxWidgets)
5. Open the properties for the Aegisub project and set the location of MSYS in Configuration Properties > Aegisub > Library paths
6. Build Aegisub
7. Copy the contents of an existing Aegisub install into the aegisub/aegisub/bin directory (not strictly required, but you'll be missing a lot of functionality otherwise).
There's a pile of other files needed at runtime such as dictionaries, VSFilter and avisynth. The simplest way to get them is to copy all of the files from the Aegisub installer to the bin directory.