MSVC deps

[GiffE]

Hey, This generator doesn't support msvc deps at the moment. https://ninja-build.org/manual.html#_deps

Currently if a depfile is provided it then writes a deps of 'gcc'.
It wouldn't be a large change to add an additional deps(type) function which provides access to what depfile type is provided.

something along the lines of (keep in mind I don't know coffeescript):

deps: (type) ->
    @deps = type
    this

 # Write the rule into a `stream`.
    write: (stream) ->
        ....
        if @dependencyFile? and @deps?
            stream.write "  depfile = #{@dependencyFile}\n"
            stream.write "  deps = #{@deps}\n"

Otherwise, great work on this generator, it has certainly helped.