When setting up a build for the first time on windows, makes it so you
no longer have to run cmake twice: once to build, then once again with
the COPY_DEPENDENCIES box to ensure dependencies are copied.
Closesjp9000/obs-studio#768
Copying this binary is kind of unnecessary because it's something that
everyone has as long as they update DirectX, and isn't something we can
distribute because it's a Microsoft DLL.
If the cmake user variable COPY_DEPENDENCIES is set, this script will
make it so that a windows build will automatically copy all required
dependencies (FFmpeg, x264, and Qt5) to the respective
additional_install_files\exec(32|64) directory. This makes it much
easier to set up a development environment on windows, and much easier
to make usable test builds.
It will also copy the appropriate Direct3D compiler DLL, along with
dependencies of dependencies (the icu*.dll and EGL/GLES files for Qt)
