contrib: Windows: add speexdsp files

Speexdsp is hardcoded into the config currently, so until that's refactored, this will fix the build.

Change-Id: I5ebd80cc7ff57cbab96929fa11127ba2d0bbb068

CMakeLists.txt

@@ -235,6 +235,7 @@ elseif(MSVC)
          "${Source_Files__media__video__uwpvideo}"
          "${Source_Files__media__video__winvideo}"
          "${Source_Files__media__audio__webrtc}"
+         "${Source_Files__media__audio__speexdsp}"
    )
 endif()