FFMPEG & VPX don't handle target with --build parameter, so we need to make sure use of plain configure command
Reviewed by: Brecht Van Lommel
Differential Revision: http://developer.blender.org/D2791
Note these are intended for platform maintainers, we do not intend to
support users making their own builds with these. For that precompiled
libraries from lib/ should be used.
Implemented by Martijn Berger, Ray Molenkamp and Brecht Van Lommel.
Differential Revision: https://developer.blender.org/D2753